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MDN JavaScript pages

This page lists all MDN JavaScript pages along with their summary and tags.

Found 862 pages:

# Page Tags and summary
1 JavaScript JavaScript, Landing, Learn, l10n:priority
JavaScript (JS) is a lightweight interpreted or JIT-compiled programming language with first-class functions. While it is most well-known as the scripting language for Web pages, many non-browser environments also use it, such as Node.js, Apache CouchDB and Adobe Acrobat.
2 A re-introduction to JavaScript (JS tutorial) CodingScripting, Guide, Intermediate, Intro, JavaScript, Learn
Why a re-introduction? Because JavaScript is notorious for being the world's most misunderstood programming language. It is often derided as being a toy, but beneath its layer of deceptive simplicity, powerful language features await. JavaScript is now used by an incredible number of high-profile applications, showing that deeper knowledge of this technology is an important skill for any web or mobile developer.
3 About JavaScript Beginner, Introduction, JavaScript
JavaScript® (often shortened to JS) is a lightweight, interpreted, object-oriented language with first-class functions, and is best known as the scripting language for Web pages, but it's used in many non-browser environments as well. It is a prototype-based, multi-paradigm scripting language that is dynamic, and supports object-oriented, imperative, and functional programming styles.
4 Closures Closure, ES5, Intermediate, JavaScript, Reference
A closure is the combination of a function and the lexical environment within which that function was declared.
5 Concurrency model and Event Loop Advanced, Event Loop, Event Management, Event Queue, Handling Events, JavaScript, events
JavaScript has a concurrency model based on an "event loop". This model is quite different from models in other languages like C and Java.
6 Differential inheritance in JavaScript JavaScript
Differential Inheritance is a common prototype-oriented model that uses the concept that most objects are derived from other, more generic objects, and only differ in a few small aspects. Each object maintains a reference to its prototype and a table of properties that are different.
7 Enumerability and ownership of properties JavaScript
Enumerable properties are those properties whose internal enumerable flag is set to true, which is the default for properties created via simple assignment or via a property initializer (properties defined via Object.defineProperty and such default enumerable to false). Enumerable properties show up in for...in loops unless the property's key is a Symbol. Ownership of properties is determined by whether the property belongs to the object directly and not to its prototype chain. Properties of an object can also be retrieved in total. There are a number of built-in means of detecting, iterating/enumerating, and retrieving object properties, with the chart showing which are available. Some sample code follows which demonstrates how to obtain the missing categories.
8 Equality comparisons and sameness Comparison, Equality, Intermediate, JS, JavaScript, NaN, SameValue, SameValueZero, Sameness
There are four equality algorithms in ES2015:
9 Index Index, JavaScript, MDN Meta
This page lists all MDN JavaScript pages along with their summary and tags.
10 Inheritance and the prototype chain Advanced, Guide, Inheritance, JavaScript, OOP
JavaScript is a bit confusing for developers experienced in class-based languages (like Java or C++), as it is dynamic and does not provide a class implementation per se (the class keyword is introduced in ES2015, but is syntactical sugar, JavaScript remains prototype-based).
11 Introduction to using XPath in JavaScript Add-ons, DOM, Extensions, JavaScript, Transforming_XML_with_XSLT, Web Development, XML, XPath, XSLT
This document describes the interface for using XPath in JavaScript internally, in extensions, and from websites. Mozilla implements a fair amount of the DOM 3 XPath, which means that XPath expressions can be run against both HTML and XML documents.
12 JavaScript Guide Guide, JavaScript, l10n:priority
The JavaScript Guide shows you how to use JavaScript and gives an overview of the language. If you need exhaustive information about a language feature, have a look at the JavaScript reference.
13 Control flow and error handling Beginner, Guide, JavaScript, l10n:priority
JavaScript supports a compact set of statements, specifically control flow statements, that you can use to incorporate a great deal of interactivity in your application. This chapter provides an overview of these statements.
14 Details of the object model Guide, Intermediate, JavaScript, Object, l10n:priority
JavaScript is an object-based language based on prototypes, rather than being class-based. Because of this different basis, it can be less apparent how JavaScript allows you to create hierarchies of objects and to have inheritance of properties and their values. This chapter attempts to clarify the situation.
15 Expressions and operators Beginner, Expressions, Guide, JavaScript, Operators, l10n:priority
This chapter describes JavaScript's expressions and operators, including assignment, comparison, arithmetic, bitwise, logical, string, ternary and more.
16 Functions Beginner, Functions, Guide, JavaScript, l10n:priority
Functions are one of the fundamental building blocks in JavaScript. A function is a JavaScript procedure—a set of statements that performs a task or calculates a value. To use a function, you must define it somewhere in the scope from which you wish to call it.
17 Grammar and types Guide, JavaScript, l10n:priority
This chapter discusses JavaScript's basic grammar, variable declarations, data types and literals.
18 Indexed collections Guide, JavaScript, Method, l10n:priority
This chapter introduces collections of data which are ordered by an index value. This includes arrays and array-like constructs such as Array objects and TypedArray objects.
19 Introduction Beginner, Guide, Introduction, JavaScript, l10n:priority
This chapter introduces JavaScript and discusses some of its fundamental concepts.
20 Iterators and generators Guide, Intermediate, JavaScript, l10n:priority
Processing each of the items in a collection is a very common operation. JavaScript provides a number of ways of iterating over a collection, from simple for loops to map() and filter(). Iterators and Generators bring the concept of iteration directly into the core language and provide a mechanism for customizing the behavior of for...of loops.
21 Keyed collections Collections, Guide, JavaScript, Map, l10n:priority, set
This chapter introduces collections of data which are ordered by a key; Map and Set objects contain elements which are iterable in the order of insertion.
22 Loops and iteration Guide, JavaScript, Loop, Syntax, l10n:priority
Loops offer a quick and easy way to do something repeatedly. This chapter of the JavaScript Guide introduces the different iteration statements available to JavaScript.
23 Meta programming Guide, JavaScript, Proxy, Reflect, l10n:priority
Starting with ECMAScript 2015, JavaScript gains support for the Proxy and Reflect objects allowing you to intercept and define custom behavior for fundamental language operations (e.g. property lookup, assignment, enumeration, function invocation, etc). With the help of these two objects you are able to program at the meta level of JavaScript.
24 Numbers and dates Guide, JavaScript, l10n:priority
This chapter introduces how to work with numbers and dates in JavaScript.
25 Regular Expressions Guide, Intermediate, JavaScript, Reference, RegExp, Regular Expressions, regex
Regular expressions are patterns used to match character combinations in strings. In JavaScript, regular expressions are also objects. These patterns are used with the exec and test methods of RegExp, and with the match, replacesearch, and split methods of String. This chapter describes JavaScript regular expressions.
26 Text formatting Guide, JavaScript, l10n:priority
This chapter introduces how to work with strings and text in JavaScript.
27 Using promises Guide, Intermediate, JavaScript, Promise, Promises, asynchronous, l10n:priority
A Promise is an object representing the eventual completion or failure of an asynchronous operation. Since most people are consumers of already-created promises, this guide will explain consumption of returned promises before explaining how to create them.
28 Working with objects Beginner, Comparing object, Constructor, Document, Guide, JavaScript, Object, l10n:priority
JavaScript is designed on a simple object-based paradigm. An object is a collection of properties, and a property is an association between a name (or key) and a value. A property's value can be a function, in which case the property is known as a method. In addition to objects that are predefined in the browser, you can define your own objects. This chapter describes how to use objects, properties, functions, and methods, and how to create your own objects.
29 JavaScript data types and data structures Beginner, JavaScript, Types
Programming languages all have built-in data structures, but these often differ from one language to another. This article attempts to list the built-in data structures available in JavaScript and what properties they have; these can be used to build other data structures. Wherever possible, comparisons with other languages are drawn.
30 JavaScript language resources Advanced, JavaScript
ECMAScript is the scripting language that forms the basis of JavaScript. ECMAScript standardized by the ECMA International standards organization in the ECMA-262 and ECMA-402 specifications. The following ECMAScript standards have been approved or are being worked on:
31 JavaScript reference JavaScript, l10n:priority
This part of the JavaScript section on MDN serves as a repository of facts about the JavaScript language. Read more about this reference.
32 About the JavaScript reference JavaScript
The JavaScript reference serves as a repository of facts about the JavaScript language. The entire language is described here in detail. As you write JavaScript code, you'll refer to these pages often (thus the title "JavaScript reference"). If you're learning JavaScript, or need help understanding some of its capabilities or features, check out the JavaScript guide.
33 Classes Classes, Constructors, ECMAScript 2015, Inheritance, Intermediate, JavaScript
JavaScript classes, introduced in ECMAScript 2015, are primarily syntactical sugar over JavaScript's existing prototype-based inheritance. The class syntax does not introduce a new object-oriented inheritance model to JavaScript.
34 constructor Classes, ECMAScript 2015, JavaScript
The constructor method is a special method for creating and initializing an object created within a class.
35 extends Classes, ECMAScript 2015, JavaScript
The extends keyword is used in class declarations or class expressions to create a class which is a child of another class.
36 static Classes, ECMAScript 2015, JavaScript, Static
The static keyword defines a static method for a class. Static methods aren't called on instances of the class. Instead, they're called on the class itself.
37 Deprecated and obsolete features Deprecated, JavaScript, Obsolete
This page lists features of JavaScript that are deprecated (that is, still available but planned for removal) and obsolete (that is, no longer usable).
38 The legacy Iterator protocol ES2015, JavaScript, Legacy Iterator
Firefox, prior to version 26 implemented another iterator protocol that is similar to the standard ES2015 Iterator protocol.
39 Expressions and operators JavaScript, Operators, Overview, Reference
This chapter documents all the JavaScript language operators, expressions and keywords.
40 Arithmetic operators JavaScript, Operator
Arithmetic operators take numerical values (either literals or variables) as their operands and return a single numerical value. The standard arithmetic operators are addition (+), subtraction (-), multiplication (*), and division (/).
41 Array comprehensions JavaScript, Non-standard, Obsolete, Operator, Reference
The array comprehension syntax was a JavaScript expression which allowed you to quickly assemble a new array based on an existing one. However, it has been removed from the standard and the Firefox implementation. Do not use it!
42 Assignment operators JavaScript, Operator
An assignment operator assigns a value to its left operand based on the value of its right operand.
43 Bitwise operators JavaScript, Operator, Reference
Bitwise operators treat their operands as a sequence of 32 bits (zeroes and ones), rather than as decimal, hexadecimal, or octal numbers. For example, the decimal number nine has a binary representation of 1001. Bitwise operators perform their operations on such binary representations, but they return standard JavaScript numerical values.
44 Comma operator JavaScript, Operator
The comma operator evaluates each of its operands (from left to right) and returns the value of the last operand.
45 Comparison operators JavaScript, Operator, Reference
JavaScript has both strict and type–converting comparisons. A strict comparison (e.g., ===) is only true if the operands are of the same type and the contents match. The more commonly-used abstract comparison (e.g. ==) converts the operands to the same type before making the comparison. For relational abstract comparisons (e.g., <=), the operands are first converted to primitives, then to the same type, before comparison.
46 Conditional (ternary) Operator JavaScript, Operator
The conditional (ternary) operator is the only JavaScript operator that takes three operands. This operator is frequently used as a shortcut for the if statement.
47 Destructuring assignment Destructuring, ECMAScript 2015, JavaScript, Operator
The destructuring assignment syntax is a JavaScript expression that makes it possible to unpack values from arrays, or properties from objects, into distinct variables.
48 Expression closures Function, JavaScript, Non-standard, Obsolete, Operator, Reference
Expression closures are a shorthand function syntax for writing simple functions.
49 Generator comprehensions Iterator, JavaScript, Non-standard, Obsolete, Reference
The generator comprehension syntax was a JavaScript expression which allowed you to quickly assemble a new generator function based on an existing iterable object. However, it has been removed from the standard and the Firefox implementation. Do not use it!
50 Grouping operator JavaScript, Operator, Primary Expressions
The grouping operator ( ) controls the precedence of evaluation in expressions.
51 Legacy generator function expression JavaScript, Legacy Iterator, Non-standard, Obsolete, Operator, Reference
The function keyword can be used to define a legacy generator function inside an expression. To make the function a legacy generator, the function body should contain at least one yield expression.
52 Logical Operators JavaScript, Logic, Logical Operators, Not, Operator, Reference, and, or
Logical operators are typically used with Boolean (logical) values. When they are, they return a Boolean value. However, the && and || operators actually return the value of one of the specified operands, so if these operators are used with non-Boolean values, they may return a non-Boolean value.
53 Object initializer ECMAScript 2015, JSON, JavaScript, Literal, Methods, Object, Primary Expression, computed, mutation, properties
Objects can be initialized using new Object(), Object.create(), or using the literal notation (initializer notation). An object initializer is a comma-delimited list of zero or more pairs of property names and associated values of an object, enclosed in curly braces ({}).
54 Operator precedence JavaScript, Operator, precedence
Operator precedence determines the way in which operators are parsed with respect to each other. Operators with higher precedence become the operands of operators with lower precedence.
55 Pipeline operator Experimental, JavaScript, Operator
The experimental pipeline operator |> (currently at stage 1) allows the creation of chained function calls in a readable manner. Basically, the pipeline operator provides syntactic sugar on a function call with a single argument allowing you to write
56 Property accessors JavaScript, Operator
Property accessors provide access to an object's properties by using the dot notation or the bracket notation.
57 Spread syntax ECMAScript 2015, Iterator, JavaScript
The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.
58 async function expression Function, JavaScript, Operator, Primary Expression
The async function keyword can be used to define async functions inside expressions.
59 await Function, JavaScript, Operator, Primary Expression
The await operator is used to wait for a Promise. It can only be used inside an async function.
60 class expression Classes, ECMAScript 2015, Expression, JavaScript, Operator, Reference
The class expression is one way to define a class in ECMAScript 2015. Similar to function expressions, class expressions can be named or unnamed. If named, the name of the class is local to the class body only. JavaScript classes use prototype-based inheritance.
61 delete operator JavaScript, Memory Management, Object, Operator, Property, Reference, Release, Unary, delete
The JavaScript delete operator removes a property from an object; if no more references to the same property are held, it is eventually released automatically.
62 function expression Function, JavaScript, Operator, Primary Expressions
The function keyword can be used to define a function inside an expression.
63 function* expression ECMAScript 2015, Function, Iterator, JavaScript, Operator, Primary Expression
The function* keyword can be used to define a generator function inside an expression.
64 in operator JavaScript, Operator, Relational Operators
The in operator returns true if the specified property is in the specified object or its prototype chain.
65 instanceof JavaScript, Object, Operator, Prototype, Relational Operators, instanceof
The instanceof operator tests whether the prototype property of a constructor appears anywhere in the prototype chain of an object.
66 new operator JavaScript, Left-hand-side expressions, Operator
The new operator creates an instance of a user-defined object type or of one of the built-in object types that has a constructor function.
67 new.target Classes, ECMAScript 2015, JavaScript, Reference
The new.target property lets you detect whether a function or constructor was called using the new operator. In constructors and functions instantiated with the new operator, new.target returns a reference to the constructor or function. In normal function calls, new.target is undefined.
68 super Classes, ECMAScript 2015, JavaScript, Left-hand-side expressions, Operator
The super keyword is used to access and call functions on an object's parent.
69 this JavaScript, Operator, Primary Expressions, Reference
A function's this keyword behaves a little differently in JavaScript compared to other languages. It also has some differences between strict mode and non-strict mode.
70 typeof JavaScript, Operator, Unary
The typeof operator returns a string indicating the type of the unevaluated operand.
71 void operator JavaScript, Operator, Unary
The void operator evaluates the given expression and then returns undefined.
72 yield ECMAScript 2015, Generators, Iterator, JavaScript, Operator
The yield keyword is used to pause and resume a generator function (function* or legacy generator function).
73 yield* ECMAScript 2015, Generators, Iterable, Iterator, JavaScript, Operator, Reference
The yield* expression is used to delegate to another generator or iterable object.
74 Functions Constructor, Function, Functions, JavaScript, Parameter, parameters
Generally speaking, a function is a "subprogram" that can be called by code external (or internal in the case of recursion) to the function. Like the program itself, a function is composed of a sequence of statements called the function body. Values can be passed to a function, and the function will return a value.
75 Arguments object Functions, JavaScript, Reference, arguments
arguments is an Array-like object accessible inside functions that contains the values of the arguments passed to that function.
76 arguments.callee Deprecated, Functions, JavaScript, Property, arguments
The arguments.callee property contains the currently executing function.
77 arguments.caller Functions, JavaScript, Obsolete, Property, arguments
The obsolete arguments.caller property used to provide the function that invoked the currently executing function. This property has been removed and no longer works.
78 arguments.length Functions, JavaScript, Property, arguments
The arguments.length property contains the number of arguments passed to the function.
79 arguments[@@iterator]() Deprecated, Functions, JavaScript, Property, arguments
The initial value of the @@iterator property is the same function object as the initial value of the Array.prototype.values property.
80 Arrow functions ECMAScript 2015, Functions, Intermediate, JavaScript, Reference
An arrow function expression has a shorter syntax than a function expression and does not have its own this, arguments, super, or new.target. These function expressions are best suited for non-method functions, and they cannot be used as constructors.
81 Default parameters ECMAScript 2015, Functions, JavaScript
Default function parameters allow named parameters to be initialized with default values if no value or undefined is passed.
82 Method definitions ECMAScript 2015, Functions, JavaScript, Object, Syntax
Starting with ECMAScript 2015, a shorter syntax for method definitions on objects initializers is introduced. It is a shorthand for a function assigned to the method's name.
83 Rest parameters Functions, JavaScript, Rest, Rest parameters
The rest parameter syntax allows us to represent an indefinite number of arguments as an array.
84 getter ECMAScript 2015, ECMAScript 5, Functions, JavaScript
The get syntax binds an object property to a function that will be called when that property is looked up.
85 setter ECMAScript 5, Functions, JavaScript
The set syntax binds an object property to a function to be called when there is an attempt to set that property.
86 Iteration protocols ECMAScript 2015, Intermediate, Iterable, Iterator, JavaScript
A couple of additions to ECMAScript 2015 aren't new built-ins or syntax, but protocols. These protocols can be implemented by any object respecting some conventions.
87 JavaScript error reference Debugging, Error, Errors, Exception, JavaScript, exceptions
Below, you'll find a list of errors which are thrown by JavaScript. These errors can be a helpful debugging aid, but the reported problem isn't always immediately clear. The pages below will provide additional details about these errors. Each error is an object based upon the Error object, and has a name and a message.
88 Error: Permission denied to access property "x" Error, Errors, JavaScript, Security
There was attempt to access an object for which you have no permission. This is likely an <iframe> element loaded from a different domain for which you violated the same-origin policy.
89 InternalError: too much recursion Errors, InternalError, JavaScript
When there is too much or infinite recursion, JavaScript will throw this error.
90 RangeError: argument is not a valid code point Errors, JavaScript, RangeError
No summary!
91 RangeError: invalid array length Errors, JavaScript, RangeError
RangeError
92 RangeError: invalid date Errors, JavaScript, RangeError
RangeError
93 RangeError: precision is out of range Errors, JavaScript, RangeError
RangeError
94 RangeError: radix must be an integer Errors, JavaScript, RangeError
RangeError
95 RangeError: repeat count must be less than infinity Errors, JavaScript, RangeError
RangeError
96 RangeError: repeat count must be non-negative Errors, JavaScript, RangeError
RangeError
97 ReferenceError: "x" is not defined Error, JavaScript, ReferenceError
ReferenceError.
98 ReferenceError: assignment to undeclared variable "x" Errors, JavaScript, ReferenceError, Strict Mode
ReferenceError warning in strict mode only.
99 ReferenceError: can't access lexical declaration`X' before initialization Errors, JavaScript, ReferenceError
ReferenceError
100 ReferenceError: deprecated caller or arguments usage Errors, JavaScript, Strict Mode, Warning
A strict-mode-only warning that a ReferenceError occurred. JavaScript execution won't be halted.
101 ReferenceError: invalid assignment left-hand side Errors, JavaScript, ReferenceError
ReferenceError.
102 ReferenceError: reference to undefined property "x" Errors, JavaScript, ReferenceError, Strict Mode
(Firefox only) ReferenceError warning which is reported only if javascript.options.strict preference is set to true.
103 SyntaxError: "0"-prefixed octal literals and octal escape seq. are deprecated Error, JavaScript, Strict Mode, SyntaxError
SyntaxError in strict mode only.
104 SyntaxError: "use strict" not allowed in function with non-simple parameters Errors, JavaScript, TypeError
SyntaxError.
105 SyntaxError: "x" is a reserved identifier Error, Errors, JavaScript, SyntaxError
SyntaxError
106 SyntaxError: JSON.parse: bad parsing Errors, JSON, JavaScript, Method, Property, SyntaxError
SyntaxError
107 SyntaxError: Malformed formal parameter Errors, JavaScript, SyntaxError
SyntaxError
108 SyntaxError: Unexpected token Errors, JavaScript, SyntaxError
SyntaxError
109 SyntaxError: Using //@ to indicate sourceURL pragmas is deprecated. Use //# instead Errors, JavaScript, Source maps
A warning that a SyntaxError occurred. JavaScript execution won't be halted.
110 SyntaxError: a declaration in the head of a for-of loop can't have an initializer Error, JavaScript, SyntaxError
SyntaxError
111 SyntaxError: applying the 'delete' operator to an unqualified name is deprecated Error, Errors, JavaScript, SyntaxError
SyntaxError in strict mode only.
112 SyntaxError: for-in loop head declarations may not have initializers Error, JavaScript, Strict Mode, SyntaxError
SyntaxError in strict mode only.
113 SyntaxError: function statement requires a name Error, Errors, JavaScript, SyntaxError
SyntaxError
114 SyntaxError: identifier starts immediately after numeric literal Error, Errors, JavaScript, SyntaxError
SyntaxError
115 SyntaxError: illegal character Error, Errors, JavaScript, SyntaxError
SyntaxError
116 SyntaxError: invalid regular expression flag "x" Error, JavaScript, SyntaxError
SyntaxError
117 SyntaxError: missing ) after argument list Errors, JavaScript, SyntaxError
SyntaxError.
118 SyntaxError: missing ) after condition Error, Errors, JavaScript, SyntaxError
SyntaxError
119 SyntaxError: missing : after property id Error, Errors, JavaScript, SyntaxError
SyntaxError
120 SyntaxError: missing ; before statement Errors, JavaScript, SyntaxError
SyntaxError.
121 SyntaxError: missing = in const declaration Error, JavaScript, SyntaxError
SyntaxError
122 SyntaxError: missing ] after element list Errors, JavaScript, SyntaxError
SyntaxError.
123 SyntaxError: missing formal parameter Error, Errors, JavaScript, SyntaxError
SyntaxError
124 SyntaxError: missing name after . operator Error, Errors, JavaScript, SyntaxError
SyntaxError
125 SyntaxError: missing variable name Error, Errors, JavaScript, SyntaxError
SyntaxError
126 SyntaxError: missing } after function body Error, Errors, JavaScript, SyntaxError
SyntaxError
127 SyntaxError: missing } after property list Errors, JavaScript, SyntaxError
SyntaxError
128 SyntaxError: redeclaration of formal parameter "x" Errors, JavaScript, SyntaxError
SyntaxError
129 SyntaxError: return not in function Errors, JavaScript, SyntaxError
SyntaxError.
130 SyntaxError: test for equality (==) mistyped as assignment (=)? Errors, JavaScript, SyntaxError
(Firefox only) SyntaxError warning which is reported only if javascript.options.strict preference is set to true.
131 SyntaxError: unterminated string literal Errors, JavaScript, SyntaxError
SyntaxError
132 TypeError: "x" has no properties Errors, JavaScript, TypeError
TypeError.
133 TypeError: "x" is (not) "y" Errors, JavaScript, TypeError
TypeError.
134 TypeError: "x" is not a constructor Errors, JavaScript, TypeError
TypeError
135 TypeError: "x" is not a function Errors, JavaScript, TypeError
TypeError.
136 TypeError: "x" is not a non-null object Error, Errors, JavaScript, TypeError
TypeError
137 TypeError: "x" is read-only Errors, JavaScript, TypeError
TypeError
138 TypeError: 'x' is not iterable Error, JavaScript, Reference, TypeError
TypeError
139 TypeError: More arguments needed Errors, JavaScript, TypeError
TypeError.
140 TypeError: Reduce of empty array with no initial value Error, JavaScript, Reference, TypeError
TypeError
141 TypeError: can't access dead object Addons, Error, Errors, JavaScript
TypeError
142 TypeError: can't access property "x" of "y" Errors, JavaScript, TypeError
TypeError.
143 TypeError: can't define property "x": "obj" is not extensible Error, Errors, JavaScript, TypeError
TypeError
144 TypeError: can't delete non-configurable array element Error, Errors, JavaScript, TypeError
TypeError
145 TypeError: can't redefine non-configurable property "x" Error, Errors, JavaScript, TypeError
TypeError
146 TypeError: cannot use 'in' operator to search for 'x' in 'y' Error, Errors, JavaScript, TypeError
TypeError
147 TypeError: cyclic object value Error, Errors, JavaScript, TypeError
TypeError
148 TypeError: invalid 'instanceof' operand 'x' Error, Errors, JavaScript, Reference, TypeError
TypeError
149 TypeError: invalid Array.prototype.sort argument Errors, JavaScript, TypeError
TypeError
150 TypeError: invalid arguments Error, Errors, JavaScript, TypeError
TypeError
151 TypeError: invalid assignment to const "x" Error, JavaScript, TypeError
TypeError
152 TypeError: property "x" is non-configurable and can't be deleted Errors, JavaScript, Strict Mode, TypeError
TypeError in strict mode only.
153 TypeError: setting getter-only property "x" Error, Errors, JavaScript, Strict Mode, TypeError
TypeError in strict mode only.
154 TypeError: variable "x" redeclares argument Errors, JavaScript, Strict Mode, TypeError
TypeError warning in strict mode only.
155 URIError: malformed URI sequence Error, Errors, JavaScript, URIError
URIError
156 Warning: -file- is being assigned a //# sourceMappingURL, but already has one Errors, JavaScript, Source maps, Warning
A warning. JavaScript execution won't be halted.
157 Warning: 08/09 is not a legal ECMA-262 octal constant Errors, JavaScript, SyntaxError, Warning
Warning. JavaScript execution won't be halted.
158 Warning: Date.prototype.toLocaleFormat is deprecated JavaScript, Warning
Warning. JavaScript execution won't be halted.
159 Warning: JavaScript 1.6's for-each-in loops are deprecated JavaScript, Warning
Warning
160 Warning: String.x is deprecated; use String.prototype.x instead JavaScript, Warning
Warning. JavaScript execution won't be halted.
161 Warning: expression closures are deprecated JavaScript, Warning
Warning. JavaScript execution won't be halted.
162 Warning: unreachable code after return statement JavaScript, Warning
Warning
163 X.prototype.y called on incompatible type Errors, JavaScript, TypeError
TypeError
164 JavaScript methods index JavaScript
This article entails a listing of all JavaScript methods documented on MDN sorted alphabetically.
165 JavaScript properties index JavaScript
This article entails a listing of all JavaScript properties documented on MDN sorted alphabetically.
166 Lexical grammar JavaScript, Keyword, Lexical Grammar, Literal
This page describes JavaScript's lexical grammar. The source text of ECMAScript scripts gets scanned from left to right and is converted into a sequence of input elements which are tokens, control characters, line terminators, comments or white space. ECMAScript also defines certain keywords and literals and has rules for automatic insertion of semicolons to end statements.
167 Standard built-in objects JavaScript, Reference
This chapter documents all of JavaScript's standard, built-in objects, including their methods and properties.
168 Array Array, Example, Global Objects, JavaScript, Reference
The JavaScript Array object is a global object that is used in the construction of arrays; which are high-level, list-like objects.
169 Array.from() Array, ECMAScript 2015, JavaScript, Method, Reference, polyfill
The Array.from() method creates a new, shallow-copied Array instance from an array-like or iterable object.
170 Array.isArray() Array, ECMAScript 5, JavaScript, Method, Reference, polyfill
The Array.isArray() method determines whether the passed value is an Array.
171 Array.length Array, JavaScript, Property, Reference
The length property of an object which is an instance of type Array sets or returns the number of elements in that array. The value is an unsigned, 32-bit integer that is always numerically greater than the highest index in the array.
172 Array.observe() Array, JavaScript, Method, Obsolete
The Array.observe() method was used for asynchronously observing changes to Arrays, similar to Object.observe() for objects. It provided a stream of changes in order of occurrence. It's equivalent to Object.observe() invoked with the accept type list ["add", "update", "delete", "splice"]. However, this API has been deprecated and removed from Browsers. You can use the more general Proxy object instead.
173 Array.of() Array, ECMAScript 2015, JavaScript, Method, polyfill
The Array.of() method creates a new Array instance with a variable number of arguments, regardless of number or type of the arguments.
174 Array.prototype Array, JavaScript, Property
Array instances inherit from Array.prototype. As with all constructors, you can change the constructor's prototype object to make changes to all Array instances. For example, you can add new methods and properties to extend all Array objects. This is used for polyfilling, for example.
175 Array.prototype.concat() Array, JavaScript, Method, Prototype, Reference
The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.
176 Array.prototype.copyWithin() Array, ECMAScript 2015, JavaScript, Method, Prototype, Reference, polyfill
The copyWithin() method shallow copies part of an array to another location in the same array and returns it, without modifying its size.
177 Array.prototype.entries() Array, ECMAScript 2015, Iterator, JavaScript, Method, Prototype
The entries() method returns a new Array Iterator object that contains the key/value pairs for each index in the array.
178 Array.prototype.every() Array, ECMAScript 5, JavaScript, Method, Prototype, polyfill
The every() method tests whether all elements in the array pass the test implemented by the provided function.
179 Array.prototype.fill() Array, ECMAScript 2015, JavaScript, Method, Prototype, polyfill
The fill() method fills all the elements of an array from a start index to an end index with a static value. The end index is not included.
180 Array.prototype.filter() Array, ECMAScript 5, JavaScript, Method, Prototype, Reference, polyfill
The filter() method creates a new array with all elements that pass the test implemented by the provided function.
181 Array.prototype.find() Array, ECMAScript 2015, JavaScript, Method, Prototype, Reference, polyfill
The find() method returns the value of the first element in the array that satisfies the provided testing function. Otherwise undefined is returned.
182 Array.prototype.findIndex() Array, ECMAScript 2015, JavaScript, Method, Prototype, Reference, polyfill
The findIndex() method returns the index of the first element in the array that satisfies the provided testing function. Otherwise -1 is returned.
183 Array.prototype.flat() Array, Experimental, JavaScript, Method, Prototype, Reference
The flat() method creates a new array with all sub-array elements concatenated into it recursively up to the specified depth.
184 Array.prototype.flatMap() Array, Experimental, JavaScript, Method, Prototype, Reference
The flatMap() method first maps each element using a mapping function, then flattens the result into a new array. It is identical to a map followed by a flat of depth 1, but flatMap is often quite useful, as merging both into one method is slightly more efficient.
185 Array.prototype.forEach() Array, ECMAScript 5, JavaScript, Method, Prototype, Reference
The forEach() method executes a provided function once for each array element.
186 Array.prototype.includes() Array, JavaScript, Method, Prototype, Reference, polyfill
The includes() method determines whether an array includes a certain element, returning true or false as appropriate.
187 Array.prototype.indexOf() Array, JavaScript, Method, Prototype, Reference, polyfill
The indexOf() method returns the first index at which a given element can be found in the array, or -1 if it is not present.
188 Array.prototype.join() Array, JavaScript, Method, Prototype, Reference
The join() method joins all elements of an array (or an array-like object) into a string and returns this string.
189 Array.prototype.keys() Array, ECMAScript 2015, Iterator, JavaScript, Method, Prototype
The keys() method returns a new Array Iterator object that contains the keys for each index in the array.
190 Array.prototype.lastIndexOf() Array, ECMAScript 5, JavaScript, Method, Prototype, polyfill
The lastIndexOf() method returns the last index at which a given element can be found in the array, or -1 if it is not present. The array is searched backwards, starting at fromIndex.
191 Array.prototype.map() Array, ECMAScript 5, JavaScript, Method, Prototype, Reference, polyfill
The map() method creates a new array with the results of calling a provided function on every element in the calling array.
192 Array.prototype.pop() Array, JavaScript, Method, Prototype, Reference
The pop() method removes the last element from an array and returns that element. This method changes the length of the array.
193 Array.prototype.push() Array, JavaScript, Method, Prototype, Reference
The push() method adds one or more elements to the end of an array and returns the new length of the array.
194 Array.prototype.reduce() Array, ECMAScript 5, JavaScript, Method, Prototype, Reduce, Reference
The reduce() method executes a reducer function (that you provide) on each member of the array resulting in a single output value.
195 Array.prototype.reduceRight() Array, ECMAScript 5, JavaScript, Method, Prototype, polyfill
The reduceRight() method applies a function against an accumulator and each value of the array (from right-to-left) to reduce it to a single value.
196 Array.prototype.reverse() Array, JavaScript, Method, Prototype
The reverse() method reverses an array in place. The first array element becomes the last, and the last array element becomes the first.
197 Array.prototype.shift() Array, JavaScript, Method, Prototype
The shift() method removes the first element from an array and returns that removed element. This method changes the length of the array.
198 Array.prototype.slice() Array, JavaScript, Method, Prototype, Reference
The slice() method returns a shallow copy of a portion of an array into a new array object selected from begin to end (end not included). The original array will not be modified.
199 Array.prototype.some() Array, ECMAScript5, JavaScript, Method, Prototype, Reference
The some() method tests whether at least one element in the array passes the test implemented by the provided function.
200 Array.prototype.sort() Array, JavaScript, Method, Prototype
The sort() method sorts the elements of an array in place and returns the array. The sort is not necessarily stable. The default sort order is according to string Unicode code points.
201 Array.prototype.splice() Array, JavaScript, Method, Prototype, Reference
The splice() method changes the contents of an array by removing existing elements and/or adding new elements.
202 Array.prototype.toLocaleString() Array, Internationalization, JavaScript, Method, Prototype
The toLocaleString() method returns a string representing the elements of the array. The elements are converted to Strings using their toLocaleString methods and these Strings are separated by a locale-specific String (such as a comma “,”).
203 Array.prototype.toSource() Array, JavaScript, Method, Prototype
The toSource() method returns a string representing the source code of the array.
204 Array.prototype.toString() Array, JavaScript, Method, Prototype
The toString() method returns a string representing the specified array and its elements.
205 Array.prototype.unshift() Array, JavaScript, Method, Prototype, Reference
The unshift() method adds one or more elements to the beginning of an array and returns the new length of the array.
206 Array.prototype.values() Array, ECMAScript 2015, Iterator, JavaScript, Method, Prototype
The values() method returns a new Array Iterator object that contains the values for each index in the array.
207 Array.prototype[@@iterator]() Array, ECMAScript 2015, Iterator, JavaScript, Method, Prototype, Reference
The initial value of the @@iterator property is the same function object as the initial value of the values() property.
208 Array.prototype[@@unscopables] Array, ECMAScript 2015, JavaScript, Property, Prototype
The @@unscopable symbol property contains property names that were not included in the ECMAScript standard prior to the ES2015 version. These properties are excluded from with statement bindings.
209 Array.unobserve() Array, JavaScript, Method, Obsolete
The Array.unobserve() method was used to remove observers set by Array.observe(), but has been deprecated and removed from Browsers. You can use the more general Proxy object instead.
210 get Array[@@species] Array, JavaScript, Method, Prototype
The Array[@@species] accessor property returns the Array constructor.
211 ArrayBuffer ArrayBuffer, Constructor, JavaScript, TypedArrays
The ArrayBuffer object is used to represent a generic, fixed-length raw binary data buffer. You cannot directly manipulate the contents of an ArrayBuffer; instead, you create one of the typed array objects or a DataView object which represents the buffer in a specific format, and use that to read and write the contents of the buffer.
212 ArrayBuffer.isView() ArrayBuffer, JavaScript, Method, TypedArrays
The ArrayBuffer.isView() method returns true if arg is one of the ArrayBuffer views, such as typed array objects or a DataView; false otherwise.
213 ArrayBuffer.prototype ArrayBuffer, JavaScript, Property
The ArrayBuffer.prototype property represents the prototype for the ArrayBuffer object.
214 ArrayBuffer.prototype.byteLength ArrayBuffer, JavaScript, Property, Prototype
The byteLength accessor property represents the length of an ArrayBuffer in bytes.
215 ArrayBuffer.prototype.slice() ArrayBuffer, JavaScript, Method, Prototype
The slice() method returns a new ArrayBuffer whose contents are a copy of this ArrayBuffer's bytes from begin, inclusive, up to end, exclusive.
216 ArrayBuffer.transfer() ArrayBuffer, Experimental, JavaScript, Method, Reference, TypedArrays
The static ArrayBuffer.transfer() method returns a new ArrayBuffer whose contents have been taken from the oldBuffer's data and then is either truncated or zero-extended by newByteLength. If newByteLength is undefined, the byteLength of the oldBuffer is used. This operation leaves oldBuffer in a detached state.
217 get ArrayBuffer[@@species] ArrayBuffer, JavaScript, Property, TypedArrays
The ArrayBuffer[@@species] accessor property returns the ArrayBuffer constructor.
218 AsyncFunction Constructor, Experimental, JavaScript, Reference
The AsyncFunction constructor creates a new async function object. In JavaScript every asynchronous function is actually an AsyncFunction object.
219 AsyncFunction.prototype Experimental, JavaScript, Property, Prototype, Reference
The AsyncFunction.prototype property represents the AsyncFunction prototype object.
220 Atomics JavaScript, Shared Memory, Specifications
The Atomics object provides atomic operations as static methods. They are used with SharedArrayBuffer objects.
221 Atomics.add() Atomics, JavaScript, Method, Shared Memory
The static Atomics.add() method adds a given value at a given position in the array and returns the old value at that position. This atomic operation guarantees that no other write happens until the modified value is written back.
222 Atomics.and() Atomics, JavaScript, Method, Shared Memory
The static Atomics.and() method computes a bitwise AND with a given value at a given position in the array, and returns the old value at that position. This atomic operation guarantees that no other write happens until the modified value is written back.
223 Atomics.compareExchange() Atomics, JavaScript, Method, Shared Memory
The static Atomics.compareExchange() method exchanges a given replacement value at a given position in the array, if a given expected value equals the old value.  It returns the old value at that position whether it was equal to the expected value or not. This atomic operation guarantees that no other write happens until the modified value is written back.
224 Atomics.exchange() Atomics, JavaScript, Method, Shared Memory
The static Atomics.exchange() method stores a given value at a given position in the array and returns the old value at that position. This atomic operation guarantees that no other write happens between the read of the old value and the write of the new value.
225 Atomics.isLockFree() Atomics, JavaScript, Method, Shared Memory
The static Atomics.isLockFree() method is used to determine whether to use locks or atomic operations. It returns true, if the given size is one of the BYTES_PER_ELEMENT property of integer TypedArray types.
226 Atomics.load() Atomics, JavaScript, Method, Shared Memory
The static Atomics.load() method returns a value at a given position in the array.
227 Atomics.notify() Atomics, JavaScript, Method, Shared Memory
The static Atomics.notify() method notifies up some agents that are sleeping in the wait queue.
228 Atomics.or() Atomics, JavaScript, Method, Shared Memory
The static Atomics.or() method computes a bitwise OR with a given value at a given position in the array, and returns the old value at that position. This atomic operation guarantees that no other write happens until the modified value is written back.
229 Atomics.store() Atomics, JavaScript, Method, Shared Memory
The static Atomics.store() method stores a given value at the given position in the array and returns that value.
230 Atomics.sub() Atomics, JavaScript, Method, Shared Memory
The static Atomics.sub() method substracts a given value at a given position in the array and returns the old value at that position. This atomic operation guarantees that no other write happens until the modified value is written back.
231 Atomics.wait() Atomics, JavaScript, Method, Shared Memory
The static Atomics.wait() method verifies that a given position in an Int32Array still contains a given value and if so sleeps, awaiting a wakeup or a timeout. It returns a string which is either "ok", "not-equal", or "timed-out".
232 Atomics.xor() Atomics, JavaScript, Method, Shared Memory
The static Atomics.xor() method computes a bitwise XOR with a given value at a given position in the array, and returns the old value at that position. This atomic operation guarantees that no other write happens until the modified value is written back.
233 Boolean Boolean, Constructor, JavaScript
The Boolean object is an object wrapper for a boolean value.
234 Boolean.prototype Boolean, JavaScript, Property, Prototype
The Boolean.prototype property represents the prototype for the Boolean constructor.
235 Boolean.prototype.toSource() Boolean, JavaScript, Method, Non-standard, Prototype
The toSource() method returns a string representing the source code of the object.
236 Boolean.prototype.toString() Boolean, JavaScript, Method, Prototype
The toString() method returns a string representing the specified Boolean object.
237 Boolean.prototype.valueOf() Boolean, JavaScript, Method, Prototype
The valueOf() method returns the primitive value of a Boolean object.
238 DataView Constructor, DataView, JavaScript, TypedArrays
The DataView view provides a low-level interface for reading and writing multiple number types in a binary ArrayBuffer, without having to care about the platform's endianness.
239 DataView.prototype DataView, JavaScript, Property
The DataView.prototype property represents the prototype for the DataView object.
240 DataView.prototype.buffer DataView, JavaScript, Property, Prototype, TypedArrays
The buffer accessor property represents the ArrayBuffer or SharedArrayBuffer referenced by the DataView at construction time.
241 DataView.prototype.byteLength DataView, JavaScript, Property, Prototype, TypedArrays
The byteLength accessor property represents the length (in bytes) of this view from the start of its ArrayBuffer or SharedArrayBuffer.
242 DataView.prototype.byteOffset DataView, JavaScript, Property, Prototype, TypedArrays
The byteOffset accessor property represents the offset (in bytes) of this view from the start of its ArrayBuffer or SharedArrayBuffer.
243 DataView.prototype.getFloat32() DataView, JavaScript, Method, Prototype, TypedArrays
The getFloat32() method gets a signed 32-bit float (float) at the specified byte offset from the start of the DataView.
244 DataView.prototype.getFloat64() DataView, JavaScript, Method, Prototype, TypedArrays
The getFloat64() method gets a signed 64-bit float (double) at the specified byte offset from the start of the DataView.
245 DataView.prototype.getInt16() DataView, JavaScript, Method, Prototype, TypedArrays
The getInt16() method gets a signed 16-bit integer (short) at the specified byte offset from the start of the DataView.
246 DataView.prototype.getInt32() DataView, JavaScript, Method, Prototype, TypedArrays
The getInt32() method gets a signed 32-bit integer (long) at the specified byte offset from the start of the DataView.
247 DataView.prototype.getInt8() DataView, JavaScript, Method, Prototype, TypedArrays
The getInt8() method gets a signed 8-bit integer (byte) at the specified byte offset from the start of the DataView.
248 DataView.prototype.getUint16() DataView, JavaScript, Method, Prototype, TypedArrays
The getUint16() method gets an unsigned 16-bit integer (unsigned short) at the specified byte offset from the start of the DataView.
249 DataView.prototype.getUint32() DataView, JavaScript, Method, Prototype, TypedArrays
The getUint32() method gets an unsigned 32-bit integer (unsigned long) at the specified byte offset from the start of the DataView.
250 DataView.prototype.getUint8() DataView, JavaScript, Method, Prototype, TypedArrays
The getUint8() method gets an unsigned 8-bit integer (unsigned byte) at the specified byte offset from the start of the DataView.
251 DataView.prototype.setFloat32() DataView, JavaScript, Method, Prototype, TypedArrays
The setFloat32() method stores a signed 32-bit float (float) value at the specified byte offset from the start of the DataView.
252 DataView.prototype.setFloat64() DataView, JavaScript, Method, Prototype, TypedArrays
The setFloat64() method stores a signed 64-bit float (double) value at the specified byte offset from the start of the DataView.
253 DataView.prototype.setInt16() DataView, JavaScript, Method, Prototype, TypedArrays
The setInt16() method stores a signed 16-bit integer (short) value at the specified byte offset from the start of the DataView.
254 DataView.prototype.setInt32() DataView, JavaScript, Method, Prototype, TypedArrays
The setInt32() method stores a signed 32-bit integer (long) value at the specified byte offset from the start of the DataView.
255 DataView.prototype.setInt8() DataView, JavaScript, Method, Prototype, TypedArrays
The setInt8() method stores a signed 8-bit integer (byte) value at the specified byte offset from the start of the DataView.
256 DataView.prototype.setUint16() DataView, JavaScript, Method, Prototype, TypedArrays
The setUint16() method stores an unsigned 16-bit integer (unsigned short) value at the specified byte offset from the start of the DataView.
257 DataView.prototype.setUint32() DataView, JavaScript, Method, Prototype, TypedArrays
The setUint32() method stores an unsigned 32-bit integer (unsigned long) value at the specified byte offset from the start of the DataView.
258 DataView.prototype.setUint8() DataView, JavaScript, Method, Prototype, TypedArrays
The setUint8() method stores an unsigned 8-bit integer (byte) value at the specified byte offset from the start of the DataView.
259 Date Date, JavaScript
Creates a JavaScript Date instance that represents a single moment in time. Date objects are based on a time value that is the number of milliseconds since 1 January 1970 UTC.
260 Date.UTC() Date, JavaScript, Method, Reference
The Date.UTC() method accepts the same parameters as the Date constructor, but treats them as UTC. It returns the number of milliseconds since January 1, 1970, 00:00:00 UTC.
261 Date.now() Date, JavaScript, MakeBrowserAgnostic, Method, Reference, polyfill
The Date.now() method returns the number of milliseconds elapsed since January 1, 1970 00:00:00 UTC.
262 Date.parse() Date, JavaScript, Method, Reference
The Date.parse() method parses a string representation of a date, and returns the number of milliseconds since January 1, 1970, 00:00:00 UTC or NaN if the string is unrecognized or, in some cases, contains illegal date values (e.g. 2015-02-31).
263 Date.prototype Date, JavaScript, Property, Prototype, Reference
The Date.prototype property represents the prototype for the Date constructor.
264 Date.prototype.getDate() Date, JavaScript, Method, Prototype, Reference
The getDate() method returns the day of the month for the specified date according to local time.
265 Date.prototype.getDay() Date, JavaScript, Method, Prototype, Reference
The getDay() method returns the day of the week for the specified date according to local time, where 0 represents Sunday. For the day of the month see getDate().
266 Date.prototype.getFullYear() Date, JavaScript, Method, Prototype, Reference
The getFullYear() method returns the year of the specified date according to local time.
267 Date.prototype.getHours() Date, JavaScript, Method, Prototype, Reference
The getHours() method returns the hour for the specified date, according to local time.
268 Date.prototype.getMilliseconds() Date, JavaScript, Method, Prototype, Reference
The getMilliseconds() method returns the milliseconds in the specified date according to local time.
269 Date.prototype.getMinutes() Date, JavaScript, Method, Prototype, Reference
The getMinutes() method returns the minutes in the specified date according to local time.
270 Date.prototype.getMonth() Date, JavaScript, Method, Prototype, Reference
The getMonth() method returns the month in the specified date according to local time, as a zero-based value (where zero indicates the first month of the year).
271 Date.prototype.getSeconds() Date, JavaScript, Method, Prototype, Reference
The getSeconds() method returns the seconds in the specified date according to local time.
272 Date.prototype.getTime() Date, JavaScript, Method, Prototype, Reference
The getTime() method returns the numeric value corresponding to the time for the specified date according to universal time.
273 Date.prototype.getTimezoneOffset() Date, JavaScript, Method, Prototype, Reference
The getTimezoneOffset() method returns the time zone difference, in minutes, from current locale (host system settings) to UTC.
274 Date.prototype.getUTCDate() Date, JavaScript, Method, Prototype, Reference
The getUTCDate() method returns the day (date) of the month in the specified date according to universal time.
275 Date.prototype.getUTCDay() Date, JavaScript, Method, Prototype, Reference
The getUTCDay() method returns the day of the week in the specified date according to universal time, where 0 represents Sunday.
276 Date.prototype.getUTCFullYear() Date, JavaScript, Method, Prototype, Reference
The getUTCFullYear() method returns the year in the specified date according to universal time.
277 Date.prototype.getUTCHours() Date, JavaScript, Method, Prototype, Reference
The getUTCHours() method returns the hours in the specified date according to universal time.
278 Date.prototype.getUTCMilliseconds() Date, JavaScript, Method, Prototype, Reference
The getUTCMilliseconds() method returns the milliseconds in the specified date according to universal time.
279 Date.prototype.getUTCMinutes() Date, JavaScript, Method, Prototype, Reference
The getUTCMinutes() method returns the minutes in the specified date according to universal time.
280 Date.prototype.getUTCMonth() Date, JavaScript, Method, Prototype, Reference
The getUTCMonth() returns the month of the specified date according to universal time, as a zero-based value (where zero indicates the first month of the year).
281 Date.prototype.getUTCSeconds() Date, JavaScript, Method, Prototype, Reference
The getUTCSeconds() method returns the seconds in the specified date according to universal time.
282 Date.prototype.getYear() Date, Deprecated, JavaScript, Method, Prototype, Reference
The getYear() method returns the year in the specified date according to local time. Because getYear() does not return full years ("year 2000 problem"), it is no longer used and has been replaced by the getFullYear() method.
283 Date.prototype.setDate() Date, JavaScript, Method, Prototype, Reference
The setDate() method sets the day of the Date object relative to the beginning of the currently set month.
284 Date.prototype.setFullYear() Date, JavaScript, Method, Prototype, Reference
The setFullYear() method sets the full year for a specified date according to local time. Returns new timestamp.
285 Date.prototype.setHours() Date, JavaScript, Method, Prototype, Reference
The setHours() method sets the hours for a specified date according to local time, and returns the number of milliseconds since January 1, 1970 00:00:00 UTC until the time represented by the updated Date instance.
286 Date.prototype.setMilliseconds() Date, JavaScript, Method, Prototype, Reference
The setMilliseconds() method sets the milliseconds for a specified date according to local time.
287 Date.prototype.setMinutes() Date, JavaScript, Method, Prototype, Reference
The setMinutes() method sets the minutes for a specified date according to local time.
288 Date.prototype.setMonth() Date, JavaScript, Method, Prototype, Reference
The setMonth() method sets the month for a specified date according to the currently set year.
289 Date.prototype.setSeconds() Date, JavaScript, Method, Prototype, Reference
The setSeconds() method sets the seconds for a specified date according to local time.
290 Date.prototype.setTime() Date, JavaScript, Method, Prototype, Reference
The setTime() method sets the Date object to the time represented by a number of milliseconds since January 1, 1970, 00:00:00 UTC.
291 Date.prototype.setUTCDate() Date, JavaScript, Method, Prototype, Reference
The setUTCDate() method sets the day of the month for a specified date according to universal time.
292 Date.prototype.setUTCFullYear() Date, JavaScript, Method, Prototype, Reference
The setUTCFullYear() method sets the full year for a specified date according to universal time.
293 Date.prototype.setUTCHours() Date, JavaScript, Method, Prototype, Reference
The setUTCHours() method sets the hour for a specified date according to universal time, and returns the number of milliseconds since  January 1, 1970 00:00:00 UTC until the time represented by the updated Date instance.
294 Date.prototype.setUTCMilliseconds() Date, JavaScript, Method, Prototype, Reference
The setUTCMilliseconds() method sets the milliseconds for a specified date according to universal time.
295 Date.prototype.setUTCMinutes() Date, JavaScript, Method, Prototype, Reference
The setUTCMinutes() method sets the minutes for a specified date according to universal time.
296 Date.prototype.setUTCMonth() Date, JavaScript, Method, Prototype, Reference
The setUTCMonth() method sets the month for a specified date according to universal time.
297 Date.prototype.setUTCSeconds() Date, JavaScript, Method, Prototype, Reference
The setUTCSeconds() method sets the seconds for a specified date according to universal time.
298 Date.prototype.setYear() Date, Deprecated, JavaScript, Method, Prototype, Reference
The setYear() method sets the year for a specified date according to local time. Because setYear() does not set full years ("year 2000 problem"), it is no longer used and has been replaced by the setFullYear() method.
299 Date.prototype.toDateString() Date, JavaScript, Method, Prototype, Reference
The toDateString() method returns the date portion of a Date object in human readable form in American English.
300 Date.prototype.toGMTString() Date, Deprecated, JavaScript, Method, Prototype, Reference
The toGMTString() method converts a date to a string, using Internet Greenwich Mean Time (GMT) conventions. The exact format of the value returned by toGMTString() varies according to the platform and browser, in general it should represent a human readable date string.
301 Date.prototype.toISOString() Date, JavaScript, Method, Prototype, Reference, polyfill
The toISOString() method returns a string in simplified extended ISO format (ISO 8601), which is always 24 or 27 characters long (YYYY-MM-DDTHH:mm:ss.sssZ or ±YYYYYY-MM-DDTHH:mm:ss.sssZ, respectively). The timezone is always zero UTC offset, as denoted by the suffix "Z".
302 Date.prototype.toJSON() Date, JavaScript, Method, Prototype, Reference
The toJSON() method returns a string representation of the Date object.
303 Date.prototype.toLocaleDateString() Date, IANA Timezone Format, Internationalization, JavaScript, Method, Prototype, Reference
The toLocaleDateString() method returns a string with a language sensitive representation of the date portion of this date. The new locales and options arguments let applications specify the language whose formatting conventions should be used and allow to customize the behavior of the function. In older implementations, which ignore the locales and options arguments, the locale used and the form of the string returned are entirely implementation dependent.
304 Date.prototype.toLocaleFormat() Date, JavaScript, Method, Non-standard, Prototype, Reference
The non-standard toLocaleFormat() method converts a date to a string using the specified formatting. Intl.DateTimeFormat is an alternative to format dates in a standards-compliant way. See also the newer version of Date.prototype.toLocaleDateString().
305 Date.prototype.toLocaleString() Date, Internationalization, JavaScript, Method, Prototype, Reference
The toLocaleString() method returns a string with a language sensitive representation of this date. The new locales and options arguments let applications specify the language whose formatting conventions should be used and customize the behavior of the function. In older implementations, which ignore the locales and options arguments, the locale used and the form of the string returned are entirely implementation dependent.
306 Date.prototype.toLocaleTimeString() Date, Internationalization, JavaScript, Method, Prototype, Reference
The toLocaleTimeString() method returns a string with a language sensitive representation of the time portion of this date. The new locales and options arguments let applications specify the language whose formatting conventions should be used and customize the behavior of the function. In older implementations, which ignore the locales and options arguments, the locale used and the form of the string returned are entirely implementation dependent.
307 Date.prototype.toSource() Date, JavaScript, Method, Prototype, Reference
The toSource() method returns a string representing the source code of the object.
308 Date.prototype.toString() Date, JavaScript, Method, Prototype, Reference
The toString() method returns a string representing the specified Date object.
309 Date.prototype.toTimeString() Date, JavaScript, Method, Prototype, Reference
The toTimeString() method returns the time portion of a Date object in human readable form in American English.
310 Date.prototype.toUTCString() Date, JavaScript, Method, Prototype, Reference
The toUTCString() method converts a date to a string, using the UTC time zone.
311 Date.prototype.valueOf() Date, JavaScript, Method, Prototype, Reference
The valueOf() method returns the primitive value of a Date object.
312 Date.prototype[@@toPrimitive] Date, JavaScript, Method, Prototype, Reference
The [@@toPrimitive]() method converts a Date object to a primitive value.
313 Error Error, JavaScript, Reference
The Error constructor creates an error object. Instances of Error objects are thrown when runtime errors occur. The Error object can also be used as a base object for user-defined exceptions. See below for standard built-in error types.
314 Error.prototype Error, JavaScript, Property
The Error.prototype property represents the prototype for the Error constructor.
315 Error.prototype.columnNumber Error, JavaScript, Non-standard, Property, Prototype
The columnNumber property contains the column number in the line of the file that raised this error.
316 Error.prototype.fileName Error, JavaScript, Non-standard, Property, Prototype
The fileName property contains the path to the file that raised this error.
317 Error.prototype.lineNumber Error, JavaScript, Non-standard, Property, Prototype, Reference
The lineNumber property contains the line number in the file that raised this error.
318 Error.prototype.message Error, JavaScript, Property, Prototype
The message property is a human-readable description of the error.
319 Error.prototype.name Error, JavaScript, Property, Prototype
The name property represents a name for the type of error. The initial value is "Error".
320 Error.prototype.stack Error, JavaScript, Non-standard, Property, Prototype, Reference
The non-standard stack property of Error objects offer a trace of which functions were called, in what order, from which line and file, and with what arguments. The stack string proceeds from the most recent calls to earlier ones, leading back to the original global scope call.
321 Error.prototype.toSource() Error, JavaScript, Method, Non-standard, Prototype
The toSource() method returns code that could eval to the same error.
322 Error.prototype.toString() Error, JavaScript, Method, Prototype
The toString() method returns a string representing the specified Error object.
323 EvalError Error, EvalError, JavaScript, Reference
The EvalError object indicates an error regarding the global eval() function. This exception is not thrown by JavaScript anymore, however the EvalError object remains for compatibility.
324 EvalError.prototype Error, EvalError, JavaScript, Property
The EvalError.prototype property represents the prototype of the EvalError constructor.
325 Float32Array Constructor, JavaScript, TypedArray, TypedArrays
The Float32Array typed array represents an array of 32-bit floating point numbers (corresponding to the C float data type) in the platform byte order. If control over byte order is needed, use DataView instead. The contents are initialized to 0. Once established, you can reference elements in the array using the object's methods, or using standard array index syntax (that is, using bracket notation).
326 Float64Array Constructor, JavaScript, TypedArray, TypedArrays
The Float64Array typed array represents an array of 64-bit floating point numbers (corresponding to the C double data type) in the platform byte order. If control over byte order is needed, use DataView instead. The contents are initialized to 0. Once established, you can reference elements in the array using the object's methods, or using standard array index syntax (that is, using bracket notation).
327 Function Constructor, Function, JavaScript
The Function constructor creates a new Function object. Calling the constructor directly can create functions dynamically, but suffers from security and similar (but far less significant) performance issues similar to eval. However, unlike eval, the Function constructor allows executing code in the global scope, prompting better programming habits and allowing for more efficient code minification.
328 Function.arguments Deprecated, Function, JavaScript, Property, arguments
The function.arguments property refers to an an array-like object corresponding to the arguments passed to a function. Use the simple variable arguments instead. This property is forbidden in strict model due to tail call optimization.
329 Function.arity Function, JavaScript, Obsolete, Property, Unimplemented
The arity property used to return the number of arguments expected by the function, however, it no longer exists and has been replaced by the Function.prototype.length property.
330 Function.caller Function, JavaScript, Property
The function.caller property returns the function that invoked the specified function. This property is forbidden in strict model due to tail call optimization.
331 Function.displayName Function, JavaScript, Non Standard, Non-standard, Property
The function.displayName property returns the display name of the function.
332 Function.length Function, JavaScript, Property
The length property indicates the number of arguments expected by the function.
333 Function.prototype Function, JavaScript, Property, Prototype
The Function.prototype property represents the Function prototype object.
334 Function.prototype.apply() Function, JavaScript, Method
The apply() method calls a function with a given this value, and arguments provided as an array (or an array-like object).
335 Function.prototype.bind() Class, ECMAScript 2015, ECMAScript 5, Function, JavaScript, Method, bind, polyfill
The bind() method creates a new function that, when called, has its this keyword set to the provided value, with a given sequence of arguments preceding any provided when the new function is called.
336 Function.prototype.call() Function, JavaScript, Method
The call() method calls a function with a given this value and arguments provided individually.
337 Function.prototype.isGenerator() Function, JavaScript, Method, Non-standard, Obsolete
The non-standard isGenerator() method used to determine whether or not a function is a generator. It has been removed from Firefox starting with version 58.
338 Function.prototype.name ECMAScript 2015, Function, JavaScript, Property
A Function object's read-only name property indicates the function's name as specified when it was created, or "anonymous" for functions created anonymously.
339 Function.prototype.toSource() Function, JavaScript, Method
The toSource() method returns a string representing the source code of the object.
340 Function.prototype.toString() Function, JavaScript, Method, Prototype
The toString() method returns a string representing the source code of the function.
341 Generator ECMAScript 2015, Generator, JavaScript, Legacy Generator, Legacy Iterator, Reference
The Generator object is returned by a generator function and it conforms to both the iterable protocol and the iterator protocol.
342 Generator.prototype.next() ECMAScript 2015, Generator, JavaScript, Method, Prototype, Reference
The next() method returns an object with two properties done and value. You can also provide a parameter to the next method to send a value to the generator.
343 Generator.prototype.return() ECMAScript 2015, Generator, JavaScript, Method, Prototype, Reference
The return() method returns the given value and finishes the generator.
344 Generator.prototype.throw() ECMAScript 2015, Generator, JavaScript, Method, Prototype, Reference
The throw() method resumes the execution of a generator by throwing an error into it and returns an object with two properties done and value.
345 GeneratorFunction Constructor, ECMAScript 2015, GeneratorFunction, Iterator, JavaScript, Reference
The GeneratorFunction constructor creates a new generator function object. In JavaScript every generator function is actually a GeneratorFunction object.
346 GeneratorFunction.prototype ECMAScript 2015, GeneratorFunction, Iterator, JavaScript, Property, Prototype, Reference
The GeneratorFunction.prototype property represents the GeneratorFunction prototype object.
347 Infinity JavaScript
The global Infinity property is a numeric value representing infinity.
348 Int16Array Constructor, JavaScript, TypedArray, TypedArrays
The Int16Array typed array represents an array of twos-complement 16-bit signed integers in the platform byte order. If control over byte order is needed, use DataView instead. The contents are initialized to 0. Once established, you can reference elements in the array using the object's methods, or using standard array index syntax (that is, using bracket notation).
349 Int32Array Constructor, JavaScript, TypedArray, TypedArrays
The Int32Array typed array represents an array of twos-complement 32-bit signed integers in the platform byte order. If control over byte order is needed, use DataView instead. The contents are initialized to 0. Once established, you can reference elements in the array using the object's methods, or using standard array index syntax (that is, using bracket notation).
350 Int8Array Constructor, Int8Array, JavaScript, TypedArray, TypedArrays
The Int8Array typed array represents an array of twos-complement 8-bit signed integers. The contents are initialized to 0. Once established, you can reference elements in the array using the object's methods, or using standard array index syntax (that is, using bracket notation).
351 InternalError Error, InternalError, JavaScript
The InternalError object indicates an error that occurred internally in the JavaScript engine. For example: "InternalError: too much recursion".
352 InternalError.prototype Error, InternalError, JavaScript, Property
The InternalError.prototype property represents the prototype of the InternalError constructor.
353 Intl Internationalization, JavaScript
The Intl object is the namespace for the ECMAScript Internationalization API, which provides language sensitive string comparison, number formatting, and date and time formatting. The constructors for Collator, NumberFormat, and DateTimeFormat objects are properties of the Intl object. This page documents these properties as well as functionality common to the internationalization constructors and other language sensitive functions.
354 Intl.getCanonicalLocales() Internationalization, Intl, JavaScript, Method
The Intl.getCanonicalLocales() method returns an array containing the canonical locale names. Duplicates will be omitted and elements will be validated as structurally valid language tags.
355 Intl.Collator Collator, Internationalization, JavaScript
The Intl.Collator object is a constructor for collators, objects that enable language sensitive string comparison.
356 Intl.Collator.prototype Collator, Internationalization, JavaScript, Property, Prototype
The Intl.Collator.prototype property represents the prototype object for the Intl.Collator constructor.
357 Intl.Collator.prototype.compare Collator, Internationalization, JavaScript, Property, Prototype
The Intl.Collator.prototype.compare property returns a function that compares two strings according to the sort order of this Collator object.
358 Intl.Collator.prototype.resolvedOptions() Collator, Internationalization, JavaScript, Method, Prototype
The Intl.Collator.prototype.resolvedOptions() method returns a new object with properties reflecting the locale and collation options computed during initialization of this Collator object.
359 Intl.Collator.supportedLocalesOf() Collator, Internationalization, JavaScript, Method
The Intl.Collator.supportedLocalesOf() method returns an array containing those of the provided locales that are supported in collation without having to fall back to the runtime's default locale.
360 Intl.DateTimeFormat DateTimeFormat, Internationalization, JavaScript
The Intl.DateTimeFormat object is a constructor for objects that enable language-sensitive date and time formatting.
361 Intl.DateTimeFormat.prototype DateTimeFormat, Internationalization, JavaScript, Property, Prototype
The Intl.DateTimeFormat.prototype property represents the prototype object for the Intl.DateTimeFormat constructor.
362 Intl.DateTimeFormat.prototype.format DateTimeFormat, Internationalization, JavaScript, Property, Prototype
The Intl.DateTimeFormat.prototype.format property returns a getter function that formats a date according to the locale and formatting options of this Intl.DateTimeFormat object.
363 Intl.DateTimeFormat.prototype.formatToParts() DateTimeFormat, Internationalization, Intl, JavaScript, Method, Prototype
The Intl.DateTimeFormat.prototype.formatToParts() method allows locale-aware formatting of strings produced by DateTimeFormat formatters.
364 Intl.DateTimeFormat.prototype.resolvedOptions() DateTimeFormat, Internationalization, JavaScript, Method, Prototype
The Intl.DateTimeFormat.prototype.resolvedOptions() method returns a new object with properties reflecting the locale and date and time formatting options computed during initialization of this DateTimeFormat object.
365 Intl.DateTimeFormat.supportedLocalesOf() DateTimeFormat, Internationalization, JavaScript, Method, Prototype
The Intl.DateTimeFormat.supportedLocalesOf() method returns an array containing those of the provided locales that are supported in date and time formatting without having to fall back to the runtime's default locale.
366 Intl.NumberFormat Internationalization, JavaScript, NumberFormat
The Intl.NumberFormat object is a constructor for objects that enable language sensitive number formatting.
367 Intl.NumberFormat.prototype Internationalization, JavaScript, NumberFormat, Property, Prototype
The Intl.NumberFormat.prototype property represents the prototype object for the Intl.NumberFormat constructor.
368 Intl.NumberFormat.prototype.format Internationalization, JavaScript, NumberFormat, Property, Prototype
The Intl.NumberFormat.prototype.format property returns a getter function that formats a number according to the locale and formatting options of this NumberFormat object.
369 Intl.NumberFormat.prototype.formatToParts() Internationalization, Intl, JavaScript, Method, NumberFormat, Prototype
The Intl.Numberformat.prototype.formatToParts() method allows locale-aware formatting of strings produced by NumberTimeFormat formatters.
370 Intl.NumberFormat.prototype.resolvedOptions() Internationalization, JavaScript, Method, NumberFormat, Prototype
The Intl.NumberFormat.prototype.resolvedOptions() method returns a new object with properties reflecting the locale and number formatting options computed during initialization of this NumberFormat object.
371 Intl.NumberFormat.supportedLocalesOf() Internationalization, JavaScript, Method, NumberFormat
The Intl.NumberFormat.supportedLocalesOf() method returns an array containing those of the provided locales that are supported in number formatting without having to fall back to the runtime's default locale.
372 Intl.PluralRules Internationalization, Intl, JavaScript, PluralRules
The Intl.PluralRules object is a constructor for objects that enable plural sensitive formatting and plural language rules.
373 Intl.PluralRules.prototype Internationalization, Intl, JavaScript, Property, Prototype
The Intl.PluralRules.prototype property represents the prototype object for the Intl.PluralRules constructor.
374 Intl.PluralRules.prototype.resolvedOptions() Internationalization, Intl, JavaScript, Method, PluralRules, Prototype
The Intl.PluralRules.prototype.resolvedOptions() method returns a new object with properties reflecting the locale and plural formatting options computed during initialization of this PluralRules object.
375 Intl.PluralRules.select() Internationalization, Intl, JavaScript, Method, PluralRules
The Intl.PluralRules.prototype.select method returns a String indicating which plural rule to use for locale-aware formatting.
376 Intl.PluralRules.supportedLocalesOf() Internationalization, Intl, JavaScript, Method, PluralRules
The Intl.PluralRules.supportedLocalesOf() method returns an array containing those of the provided locales that are supported in plural formatting without having to fall back to the runtime's default locale.
377 JSON JSON, JavaScript, Object, Reference
The JSON object contains methods for parsing JavaScript Object Notation (JSON) and converting values to JSON. It can't be called or constructed, and aside from its two method properties, it has no interesting functionality of its own.
378 JSON.parse() ECMAScript 5, JSON, JavaScript, Method, Reference
The JSON.parse() method parses a JSON string, constructing the JavaScript value or object described by the string. An optional reviver function can be provided to perform a transformation on the resulting object before it is returned.
379 JSON.stringify() JSON, JavaScript, Method, Objects, Reference, stringify
The JSON.stringify() method converts a JavaScript value to a JSON string, optionally replacing values if a replacer function is specified or optionally including only the specified properties if a replacer array is specified.
380 Map ECMAScript 2015, JavaScript, Map
The Map object holds key-value pairs.
381 Map.prototype ECMAScript 2015, JavaScript, Map, Property
The Map.prototype property represents the prototype for the Map constructor.
382 Map.prototype.clear() ECMAScript 2015, JavaScript, Map, Method, Prototype
The clear() method removes all elements from a Map object.
383 Map.prototype.delete() ECMAScript 2015, JavaScript, Map, Method, Prototype, Reference
The delete() method removes the specified element from a Map object.
384 Map.prototype.entries() ECMAScript 2015, Iterator, JavaScript, Map, Method, Prototype
The entries() method returns a new Iterator object that contains the [key, value] pairs for each element in the Map object in insertion order.
385 Map.prototype.forEach() ECMAScript 2015, JavaScript, Map, Method, Prototype
The forEach() method executes a provided function once per each key/value pair in the Map object, in insertion order.
386 Map.prototype.get() ECMAScript 2015, JavaScript, Map, Method, Prototype
The get() method returns a specified element from a Map object.
387 Map.prototype.has() ECMAScript 2015, JavaScript, Map, Method, Prototype
The has() method returns a boolean indicating whether an element with the specified key exists or not.
388 Map.prototype.keys() ECMAScript 2015, Iterator, JavaScript, Map, Method, Prototype
The keys() method returns a new Iterator object that contains the keys for each element in the Map object in insertion order.
389 Map.prototype.set() ECMAScript 2015, JavaScript, Map, Method, Prototype
The set() method adds or updates an element with a specified key and value to a Map object.
390 Map.prototype.size ECMAScript 2015, JavaScript, Map, Property
The size accessor property returns the number of elements in a Map object.
391 Map.prototype.values() ECMAScript 2015, Iterator, JavaScript, Map, Method, Prototype
The values() method returns a new Iterator object that contains the values for each element in the Map object in insertion order.
392 Map.prototype[@@iterator]() ECMAScript 2015, Iterator, JavaScript, Map, Method, Prototype, Reference
The initial value of the @@iterator property is the same function object as the initial value of the entries method.
393 Map.prototype[@@toStringTag] ECMAScript 2015, JavaScript, Map, Property, Prototype, Reference
The Map[@@toStringTag] property has an initial value of "Map".
394 get Map[@@species] ECMAScript 2015, JavaScript, Map, Property
The Map[@@species] accessor property returns the Map constructor.
395 Math JavaScript, Math, Reference
Math is a built-in object that has properties and methods for mathematical constants and functions. Not a function object.
396 Math.E JavaScript, Math, Property, Reference
The Math.E property represents the base of natural logarithms, e, approximately 2.718.
397 Math.LN10 JavaScript, Math, Property, Reference
The Math.LN10 property represents the natural logarithm of 10, approximately 2.302:
398 Math.LN2 JavaScript, Math, Property, Reference
The Math.LN2 property represents the natural logarithm of 2, approximately 0.693:
399 Math.LOG10E JavaScript, Math, Property, Reference
The Math.LOG10E property represents the base 10 logarithm of e, approximately 0.434:
400 Math.LOG2E JavaScript, Math, Property, Reference
The Math.LOG2E property represents the base 2 logarithm of e, approximately 1.442:
401 Math.PI JavaScript, Math, Property, Reference
The Math.PI property represents the ratio of the circumference of a circle to its diameter, approximately 3.14159:
402 Math.SQRT1_2 JavaScript, Math, Property, Reference
The Math.SQRT1_2 property represents the square root of 1/2 which is approximately 0.707:
403 Math.SQRT2 JavaScript, Math, Property, Reference
The Math.SQRT2 property represents the square root of 2, approximately 1.414:
404 Math.abs() JavaScript, Math, Method, Reference
The Math.abs() function returns the absolute value of a number, that is
405 Math.acos() JavaScript, Math, Method, Reference
The Math.acos() function returns the arccosine (in radians) of a number, that is
406 Math.acosh() JavaScript, Math, Method, Reference
The Math.acosh() function returns the hyperbolic arc-cosine of a number, that is
407 Math.asin() JavaScript, Math, Method, Reference
The Math.asin() function returns the arcsine (in radians) of a number, that is
408 Math.asinh() JavaScript, Math, Method, Reference
The Math.asinh() function returns the hyperbolic arcsine of a number, that is
409 Math.atan() JavaScript, Math, Method, Reference
The Math.atan() function returns the arctangent (in radians) of a number, that is
410 Math.atan2() JavaScript, Math, Method, Reference
The Math.atan2() function returns the angle in the plane (in radians) between the positive x-axis and the ray from (0,0) to the point (x,y), for Math.atan2(y,x).
411 Math.atanh() JavaScript, Math, Method, Reference
The Math.atanh() function returns the hyperbolic arctangent of a number, that is
412 Math.cbrt() JavaScript, Math, Method, Reference
The Math.cbrt() function returns the cube root of a number, that is
413 Math.ceil() JavaScript, Math, Method, Reference
The Math.ceil() function returns the smallest integer greater than or equal to a given number.
414 Math.clz32() ECMAScript 2015, JavaScript, Math, Method, Reference
The Math.clz32() function returns the number of leading zero bits in the 32-bit binary representation of a number.
415 Math.cos() Geometry, JavaScript, Math, Method, Reference, Trigonometry, cos, cosine
The Math.cos() static function returns the cosine of the specified angle, which must be specified in radians. This value is
416 Math.cosh() JavaScript, Math, Method, Reference
The Math.cosh() function returns the hyperbolic cosine of a number, that can be expressed using the constant e:
417 Math.exp() JavaScript, Math, Method, Reference
The Math.exp() function returns ex, where x is the argument, and e is Euler's number (also known as Napier's constant), the base of the natural logarithms.
418 Math.expm1() JavaScript, Math, Method, Reference
The Math.expm1() function returns ex - 1, where x is the argument, and e the base of the natural logarithms.
419 Math.floor() JavaScript, Math, Method, Reference
The Math.floor() function returns the largest integer less than or equal to a given number.
420 Math.fround() JavaScript, Math, Method, Reference, fround
The Math.fround() function returns the nearest 32-bit single precision float representation of a Number.
421 Math.hypot() JavaScript, Math, Method, Reference
The Math.hypot() function returns the square root of the sum of squares of its arguments, that is
422 Math.imul() JavaScript, Math, Method, Reference, imul
The Math.imul() function returns the result of the C-like 32-bit multiplication of the two parameters.
423 Math.log() JavaScript, Math, Method, Reference
The Math.log() function returns the natural logarithm (base e) of a number, that is
424 Math.log10() ECMAScript 2015, JavaScript, Math, Method, Reference
The Math.log10() function returns the base 10 logarithm of a number, that is
425 Math.log1p() ECMAScript 2015, JavaScript, Math, Method, Reference
The Math.log1p() function returns the natural logarithm (base e) of 1 + a number, that is
426 Math.log2() ECMAScript 2015, JavaScript, Math, Method, Reference
The Math.log2() function returns the base 2 logarithm of a number, that is
427 Math.max() JavaScript, Math, Method, Reference
The Math.max() function returns the largest of zero or more numbers.
428 Math.min() JavaScript, Lowest Number, Lowest Value, Math, Method, Minimum, Reference, Smallest, Smallest Number, Smallest Value, min
The static function Math.min() returns the lowest-valued number passed into it, or NaN if any parameter isn't a number and can't be converted into one.
429 Math.pow() JavaScript, Math, Method, Reference
The Math.pow() function returns the base to the exponent power, that is, baseexponent.
430 Math.random() JavaScript, Math, Method, Reference
The Math.random() function returns a floating-point, pseudo-random number in the range 0–1 (inclusive of 0, but not 1) with approximately uniform distribution over that range — which you can then scale to your desired range. The implementation selects the initial seed to the random number generation algorithm; it cannot be chosen or reset by the user.
431 Math.round() JavaScript, Math, Method, Number, Reference
The Math.round() function returns the value of a number rounded to the nearest integer.
432 Math.sign() JavaScript, Math, Method, Reference
The Math.sign() function returns the sign of a number, indicating whether the number is positive, negative or zero.
433 Math.sin() JavaScript, Math, Method, Reference
The Math.sin() function returns the sine of a number.
434 Math.sinh() ECMAScript 2015, JavaScript, Math, Method, Reference
The Math.sinh() function returns the hyperbolic sine of a number, that can be expressed using the constant e:
435 Math.sqrt() JavaScript, Math, Method, Reference
The Math.sqrt() function returns the square root of a number, that is
436 Math.tan() JavaScript, Math, Method, Reference
The Math.tan() function returns the tangent of a number.
437 Math.tanh() ECMAScript 2015, JavaScript, Math, Method, Reference
The Math.tanh() function returns the hyperbolic tangent of a number, that is
438 Math.trunc() ECMAScript 2015, JavaScript, Math, Method, Reference
The Math.trunc() function returns the integer part of a number by removing any fractional digits.
439 NaN JavaScript, Property, Reference
The global NaN property is a value representing Not-A-Number.
440 Number JavaScript, Number, Reference
The Number JavaScript object is a wrapper object allowing you to work with numerical values. A Number object is created using the Number() constructor.
441 Number.EPSILON ECMAScript 2015, JavaScript, Number, Property
The Number.EPSILON property represents the difference between 1 and the smallest floating point number greater than 1.
442 Number.MAX_SAFE_INTEGER ECMAScript 2015, JavaScript, Number, Property
The Number.MAX_SAFE_INTEGER constant represents the maximum safe integer in JavaScript (253 - 1).
443 Number.MAX_VALUE JavaScript, Number, Property
The Number.MAX_VALUE property represents the maximum numeric value representable in JavaScript.
444 Number.MIN_SAFE_INTEGER ECMAScript 2015, JavaScript, Number, Property
The Number.MIN_SAFE_INTEGER constant represents the minimum safe integer in JavaScript (-(253 - 1)).
445 Number.MIN_VALUE JavaScript, Number, Property
The Number.MIN_VALUE property represents the smallest positive numeric value representable in JavaScript.
446 Number.NEGATIVE_INFINITY JavaScript, Number, Property
The Number.NEGATIVE_INFINITY property represents the negative Infinity value.
447 Number.NaN JavaScript, Number, Property
The Number.NaN property represents Not-A-Number. Equivalent of NaN.
448 Number.POSITIVE_INFINITY JavaScript, Number, Property
The Number.POSITIVE_INFINITY property represents the positive Infinity value.
449 Number.isFinite() JavaScript, Method, Number, Reference
The Number.isFinite() method determines whether the passed value is a finite number.
450 Number.isInteger() JavaScript, Method, Number, Reference
The Number.isInteger() method determines whether the passed value is an integer.
451 Number.isNaN() ECMAScript 2015, JavaScript, Method, Number
The Number.isNaN() method determines whether the passed value is NaN and its type is Number. It is a more robust version of the original, global isNaN().
452 Number.isSafeInteger() ECMAScript 2015, JavaScript, Method, Number
The Number.isSafeInteger() method determines whether the provided value is a number that is a safe integer.
453 Number.parseFloat() ECMAScript 2015, JavaScript, Method, Number
The Number.parseFloat() method parses a string argument and returns a floating point number. This method behaves identically to the global function parseFloat() and is part of ECMAScript 2015 (its purpose is modularization of globals).
454 Number.parseInt() ECMAScript 2015, JavaScript, Method, Number
The Number.parseInt() method parses a string argument and returns an integer of the specified radix or base.
455 Number.prototype JavaScript, Number, Property, Prototype
The Number.prototype property represents the prototype for the Number constructor.
456 Number.prototype.toExponential() JavaScript, Method, Number, Prototype
The toExponential() method returns a string representing the Number object in exponential notation.
457 Number.prototype.toFixed() JavaScript, Method, Number, Prototype
The toFixed() method formats a number using fixed-point notation.
458 Number.prototype.toLocaleString() Internationalization, JavaScript, Method, Number, Prototype
The toLocaleString() method returns a string with a language-sensitive representation of this number.
459 Number.prototype.toPrecision() JavaScript, Method, Number, Prototype
The toPrecision() method returns a string representing the Number object to the specified precision.
460 Number.prototype.toSource() JavaScript, Method, Number, Prototype
The toSource() method returns a string representing the source code of the object.
461 Number.prototype.toString() JavaScript, Method, Number, Prototype
The toString() method returns a string representing the specified Number object.
462 Number.prototype.valueOf() JavaScript, Method, Number, Prototype
The valueOf() method returns the wrapped primitive value of a Number object.
463 Number.toInteger() JavaScript, Method, Number, Obsolete
The Number.toInteger() method used to evaluate the passed value and convert it to an integer, but its implementation has been removed.
464 Object Constructor, JavaScript, Object
The Object constructor creates an object wrapper.
465 Object.assign() ECMAScript 2015, JavaScript, Method, Object, Reference, polyfill
The Object.assign() method is used to copy the values of all enumerable own properties from one or more source objects to a target object. It will return the target object.
466 Object.create() ECMAScript 5, JavaScript, Method, Object, Reference, polyfill
The Object.create() method creates a new object, using an existing object to provide the newly created object's __proto__ . (see browser console for visual evidence.)
467 Object.defineProperties() ECMAScript 5, JavaScript, Method, Object
The Object.defineProperties() method defines new or modifies existing properties directly on an object, returning the object.
468 Object.defineProperty() ECMAScript 5, JavaScript, JavaScript 1.8.5, Method, Object
The static method Object.defineProperty() defines a new property directly on an object, or modifies an existing property on an object, and returns the object.
469 Additional examples for Object.defineProperty Examples, JavaScript, Object
This page provides additional examples for Object.defineProperty().
470 Object.entries() JavaScript, Method, Object, Reference
The Object.entries() method returns an array of a given object's own enumerable property [key, value] pairs, in the same order as that provided by a for...in loop (the difference being that a for-in loop enumerates properties in the prototype chain as well).
471 Object.freeze() Change, Changeability, ECMAScript 5, JavaScript, Method, Mutability, Mutable, Object, Reference, freeze, lock
The Object.freeze() method freezes an object. A frozen object can no longer be changed; freezing an object prevents new properties from being added to it, existing properties from being removed, prevents changing the enumerability, configurability, or writability of existing properties, and prevents the values of existing properties from being changed. In addition, freezing an object also prevents its prototype from being changed. freeze() returns the same object that was passed in.
472 Object.fromEntries() JavaScript, Method, Object, Reference
The Object.fromEntries() method transforms a list of key-value pairs into an object.
473 Object.getNotifier() JavaScript, Method, Object, Obsolete
The Object.getNotifer() method was used to create an object that allows to synthetically trigger a change, but has been deprecated and removed in browsers.
474 Object.getOwnPropertyDescriptor() ECMAScript 5, JavaScript, Method, Object
The Object.getOwnPropertyDescriptor() method returns a property descriptor for an own property (that is, one directly present on an object and not in the object's prototype chain) of a given object.
475 Object.getOwnPropertyDescriptors() JavaScript, Method, Object
The Object.getOwnPropertyDescriptors() method returns all own property descriptors of a given object.
476 Object.getOwnPropertyNames() ECMAScript 5, JavaScript, JavaScript 1.8.5, Method, Object, Reference
The Object.getOwnPropertyNames() method returns an array of all properties (including non-enumerable properties except for those which use Symbol) found directly upon a given object.
477 Object.getOwnPropertySymbols() ECMAScript 2015, JavaScript, Method, Object
The Object.getOwnPropertySymbols() method returns an array of all symbol properties found directly upon a given object.
478 Object.getPrototypeOf() ECMAScript 5, JavaScript, Method, Object
The Object.getPrototypeOf() method returns the prototype (i.e. the value of the internal [[Prototype]] property) of the specified object.
479 Object.is() Comparison, Condition, Conditional, ECMAScript 2015, Equality, JavaScript, Method, Object
The Object.is() method determines whether two values are the same value.
480 Object.isExtensible() ECMAScript 5, JavaScript, JavaScript 1.8.5, Method, Object
The Object.isExtensible() method determines if an object is extensible (whether it can have new properties added to it).
481 Object.isFrozen() ECMAScript 5, JavaScript, JavaScript 1.8.5, Method, Object
The Object.isFrozen() determines if an object is frozen.
482 Object.isSealed() ECMAScript 5, JavaScript, JavaScript 1.8.5, Method, Object
The Object.isSealed() method determines if an object is sealed.
483 Object.keys() ECMAScript 5, JavaScript, JavaScript 1.8.5, Method, Object
The Object.keys() method returns an array of a given object's own property names, in the same order as we get with a normal loop.
484 Object.observe() JavaScript, Method, Object, Obsolete
The Object.observe() method was used for asynchronously observing the changes to an object. It provided a stream of changes in the order in which they occur. However, this API has been deprecated and removed from browsers. You can use the more general Proxy object instead.
485 Object.preventExtensions() ECMAScript 5, JavaScript, JavaScript 1.8.5, Method, Object
The Object.preventExtensions() method prevents new properties from ever being added to an object (i.e. prevents future extensions to the object).
486 Object.prototype JavaScript, Object, Property
The Object.prototype property represents the Object prototype object.
487 Object.prototype.__count__ JavaScript, Object, Obsolete, Property, Prototype
The __count__ property used to store the count of enumerable properties on the object, but it has been removed.
488 Object.prototype.__defineGetter__() Deprecated, JavaScript, Method, Object, Prototype
The __defineGetter__ method binds an object's property to a function to be called when that property is looked up.
489 Object.prototype.__defineSetter__() Deprecated, JavaScript, Method, Object, Prototype
The __defineSetter__ method binds an object's property to a function to be called when an attempt is made to set that property.
490 Object.prototype.__lookupGetter__() Deprecated, JavaScript, Method, Object, Prototype
The __lookupGetter__ method returns the function bound as a getter to the specified property.
491 Object.prototype.__lookupSetter__() Deprecated, JavaScript, Method, Object, Prototype
The __lookupSetter__ method returns the function bound as a setter to the specified property.
492 Object.prototype.__noSuchMethod__ JavaScript, Object, Obsolete, Property, Prototype
The __noSuchMethod__ property used to reference a function to be executed when a non-existent method is called on an object, but this function is no longer available.
493 Object.prototype.__parent__ JavaScript, Object, Obsolete, Property, Prototype
The __parent__ property used to point to an object's context, but it has been removed.
494 Object.prototype.__proto__ Deprecated, ECMAScript 2015, JavaScript, Object, Property, Prototype, Reference
The __proto__ property of Object.prototype is an accessor property (a getter function and a setter function) that exposes the internal [[Prototype]] (either an object or null) of the object through which it is accessed.
495 Object.prototype.constructor JavaScript, Object, Property, Prototype
Returns a reference to the Object constructor function that created the instance object. Note that the value of this property is a reference to the function itself, not a string containing the function's name. The value is only read-only for primitive values such as 1, true and "test".
496 Object.prototype.eval() JavaScript, Method, Object, Obsolete
The Object.eval() method used to evaluate a string of JavaScript code in the context of an object, however, this method has been removed.
497 Object.prototype.hasOwnProperty() JavaScript, Method, Object, Prototype
The hasOwnProperty() method returns a boolean indicating whether the object has the specified property as its own property (as opposed to inheriting it).
498 Object.prototype.isPrototypeOf() JavaScript, Method, Object, Prototype, Reference, isPrototype
The isPrototypeOf() method checks if an object exists in another object's prototype chain.
499 Object.prototype.propertyIsEnumerable() JavaScript, Method, Object, Prototype
The propertyIsEnumerable() method returns a Boolean indicating whether the specified property is enumerable.
500 Object.prototype.toLocaleString() JavaScript, Method, Object, Prototype
The toLocaleString() method returns a string representing the object. This method is meant to be overridden by derived objects for locale-specific purposes.
501 Object.prototype.toSource() JavaScript, Method, Non-standard, Object, Prototype
The toSource() method returns a string representing the source code of the object.
502 Object.prototype.toString() JavaScript, Method, Object, Prototype
The toString() method returns a string representing the object.
503 Object.prototype.unwatch() Debugging, Deprecated, JavaScript, Method, Object, Obsolete, Prototype, Reference
The unwatch() method removes a watchpoint set with the watch() method.
504 Object.prototype.valueOf() JavaScript, Method, Object, Prototype
The valueOf() method returns the primitive value of the specified object.
505 Object.prototype.watch() Debugging, Deprecated, JavaScript, Method, Object, Obsolete, Prototype
The watch() method watches for a property to be assigned a value and runs a function when that occurs.
506 Object.seal() ECMAScript 5, JavaScript, JavaScript 1.8.5, Method, Object
The Object.seal() method seals an object, preventing new properties from being added to it and marking all existing properties as non-configurable. Values of present properties can still be changed as long as they are writable.
507 Object.setPrototypeOf() ECMAScript 2015, JavaScript, Method, Object, Prototype
The Object.setPrototypeOf() method sets the prototype (i.e., the internal [[Prototype]] property) of a specified object to another object or null.
508 Object.unobserve() JavaScript, Method, Object, Obsolete
The Object.unobserve() method was used to remove observers set by Object.observe(), but has been deprecated and removed from Browsers. You can use the more general Proxy object instead.
509 Object.values() JavaScript, Method, Object, Reference
The Object.values() method returns an array of a given object's own enumerable property values, in the same order as that provided by a for...in loop (the difference being that a for-in loop enumerates properties in the prototype chain as well).
510 Promise ECMAScript 2015, JavaScript, Promise
The Promise object represents the eventual completion (or failure) of an asynchronous operation, and its resulting value.
511 Promise.all() ECMAScript 2015, JavaScript, Method, Promise
The Promise.all(iterable) method returns a single Promise that resolves when all of the promises in the iterable argument have resolved or when the iterable argument contains no promises. It rejects with the reason of the first promise that rejects.
512 Promise.prototype JavaScript, Promise, Property
The Promise.prototype property represents the prototype for the Promise constructor.
513 Promise.prototype.catch() ECMAScript 2015, JavaScript, Method, Promise, Prototype
The catch() method returns a Promise and deals with rejected cases only. It behaves the same as calling Promise.prototype.then(undefined, onRejected) (in fact, calling obj.catch(onRejected) internally calls obj.then(undefined, onRejected)). This means, that you have to provide onRejected function even if you want to fallback to undefined result value - for example obj.catch(() => {}).
514 Promise.prototype.finally() JavaScript, Method, Promises, Prototype, Reference, finally
The finally() method returns a Promise. When the promise is settled, whether fulfilled or rejected, the specified callback function is executed. This provides a way for code that must be executed once the Promise has been dealt with to be run whether the promise was fulfilled successfully or rejected.
515 Promise.prototype.then() ECMAScript 2015, JavaScript, Method, Promise, Prototype
The then() method returns a Promise. It takes up to two arguments: callback functions for the success and failure cases of the Promise.
516 Promise.race() ECMAScript 2015, JavaScript, Method, Promise
The Promise.race(iterable) method returns a promise that resolves or rejects as soon as one of the promises in the iterable resolves or rejects, with the value or reason from that promise.
517 Promise.reject() ECMAScript 2015, JavaScript, Method, Promise
The Promise.reject(reason) method returns a Promise object that is rejected with the given reason.
518 Promise.resolve() ECMAScript 2015, JavaScript, Method, Promise
The Promise.resolve(value) method returns a Promise object that is resolved with the given value. If the value is a promise, that promise is returned; if the value is a thenable (i.e. has a "then" method), the returned promise will "follow" that thenable, adopting its eventual state; otherwise the returned promise will be fulfilled with the value.
519 Proxy ECMAScript 2015, JavaScript, Proxy
The Proxy object is used to define custom behavior for fundamental operations (e.g. property lookup, assignment, enumeration, function invocation, etc).
520 Proxy handler ECMAScript 2015, JavaScript, Proxy
The proxy's handler object is a placeholder object which contains traps for proxies.
521 handler.apply() ECMAScript 2015, JavaScript, Method, Proxy
The handler.apply() method is a trap for a function call.
522 handler.construct() ECMAScript 2015, JavaScript, Method, Proxy
The handler.construct() method is a trap for the new operator. In order for the new operation to be valid on the resulting Proxy object, the target used to initialize the proxy must itself have a [[Construct]] internal method (i.e. new target must be valid).
523 handler.defineProperty() ECMAScript 2015, JavaScript, Method, Proxy
The handler.defineProperty() method is a trap for Object.defineProperty().
524 handler.deleteProperty() ECMAScript 2015, JavaScript, Method, Proxy
The handler.deleteProperty() method is a trap for the delete operator.
525 handler.enumerate() ECMAScript 2015, JavaScript, Method, Obsolete, Proxy
The handler.enumerate() method used to be a trap for for...in statements, but has been removed from the ECMAScript standard in ES2016 and is deprecated in browsers.
526 handler.get() ECMAScript 2015, JavaScript, Method, Proxy
The handler.get() method is a trap for getting a property value.
527 handler.getOwnPropertyDescriptor() ECMAScript 2015, JavaScript, Method, Proxy
The handler.getOwnPropertyDescriptor() method is a trap for Object.getOwnPropertyDescriptor().
528 handler.getPrototypeOf() ECMAScript 2015, JavaScript, Method, Proxy
The handler.getPrototypeOf() method is a trap for the [[GetPrototypeOf]] internal method.
529 handler.has() ECMAScript 2015, JavaScript, Method, Proxy
The handler.has() method is a trap for the in operator.
530 handler.isExtensible() ECMAScript 2015, JavaScript, Method, Proxy
The handler.isExtensible() method is a trap for Object.isExtensible().
531 handler.ownKeys() ECMAScript 2015, JavaScript, Method, Proxy
The handler.ownKeys() method is a trap for Reflect.ownKeys().
532 handler.preventExtensions() ECMAScript 2015, JavaScript, Method, Proxy
The handler.preventExtensions() method is a trap for Object.preventExtensions().
533 handler.set() ECMAScript 2015, JavaScript, Method, Proxy
The handler.set() method is a trap for setting a property value.
534 handler.setPrototypeOf() ECMAScript 2015, JavaScript, Method, Prototype, Proxy
The handler.setPrototypeOf() method is a trap for Object.setPrototypeOf().
535 Proxy.revocable() ECMAScript 2015, JavaScript, Method, Proxy
The Proxy.revocable() method is used to create a revocable Proxy object.
536 RangeError Error, JavaScript, Object, RangeError
The RangeError object indicates an error when a value is not in the set or range of allowed values.
537 RangeError.prototype Error, JavaScript, Property, Prototype, RangeError
The RangeError.prototype property represents the prototype the RangeError constructor.
538 ReferenceError Error, JavaScript, Object, Reference, ReferenceError
The ReferenceError object represents an error when a non-existent variable is referenced.
539 ReferenceError.prototype Error, JavaScript, Property, Prototype, ReferenceError
The ReferenceError.prototype property represents the prototype for the ReferenceError constructor.
540 Reflect ECMAScript 2015, JavaScript, Overview, Reflect
Reflect is a built-in object that provides methods for interceptable JavaScript operations. The methods are the same as those of proxy handlers. Reflect is not a function object, so it's not constructible.
541 Reflect.apply() ECMAScript 2015, JavaScript, Method, Reflect
The static Reflect.apply() method calls a target function with arguments as specified.
542 Reflect.construct() ECMAScript 2015, JavaScript, Method, Reflect
The static Reflect.construct() method acts like the new operator, but as a function. It is equivalent to calling new target(...args). It gives also the added option to specify a different prototype.
543 Reflect.defineProperty() ECMAScript 2015, JavaScript, Method, Reflect
The static Reflect.defineProperty() method is like Object.defineProperty() but returns a Boolean.
544 Reflect.deleteProperty() ECMAScript 2015, JavaScript, Method, Reflect
The static Reflect.deleteProperty() method allows to delete properties. It is like the delete operator as a function.
545 Reflect.enumerate() ECMAScript 2015, JavaScript, Method, Obsolete, Reflect
The static Reflect.enumerate() method used to return an iterator with the enumerable own and inherited properties of the target object, but has been removed in ECMAScript 2016 and is deprecated in browsers.
546 Reflect.get() ECMAScript 2015, JavaScript, Method, Reflect
The static Reflect.get() method works like getting a property from an object (target[propertyKey]) as a function.
547 Reflect.getOwnPropertyDescriptor() ECMAScript 2015, JavaScript, Method, Reflect
The static Reflect.getOwnPropertyDescriptor() method is similar to Object.getOwnPropertyDescriptor(). It returns a property descriptor of the given property if it exists on the object, undefined otherwise.
548 Reflect.getPrototypeOf() ECMAScript 2015, JavaScript, Method, Reflect
The static Reflect.getPrototypeOf() method is almost the same method as Object.getPrototypeOf(). It returns the prototype (i.e. the value of the internal [[Prototype]] property) of the specified object.
549 Reflect.has() ECMAScript 2015, JavaScript, Method, Reflect
The static Reflect.has() method works like the in operator as a function.
550 Reflect.isExtensible() ECMAScript 2015, JavaScript, Method, Reflect
The static Reflect.isExtensible() method determines if an object is extensible (whether it can have new properties added to it). It is similar to Object.isExtensible(), but with some differences.
551 Reflect.ownKeys() ECMAScript 2015, JavaScript, Method, Reflect
The static Reflect.ownKeys() method returns an array of the target object's own property keys.
552 Reflect.preventExtensions() ECMAScript 2015, JavaScript, Method, Reflect
The static Reflect.preventExtensions() method prevents new properties from ever being added to an object (i.e. prevents future extensions to the object). It is similar to Object.preventExtensions(), but with some differences.
553 Reflect.set() ECMAScript 2015, JavaScript, Method, Reflect
The static Reflect.set() method works like setting a property on an object.
554 Reflect.setPrototypeOf() ECMAScript 2015, JavaScript, Method, Reflect
The static Reflect.setPrototypeOf() method is the same method as Object.setPrototypeOf(). It sets the prototype (i.e., the internal [[Prototype]] property) of a specified object to another object or to null.
555 RegExp Constructor, JavaScript, Reference, RegExp, Regular Expressions
The RegExp constructor creates a regular expression object for matching text with a pattern.
556 RegExp.$1-$9 JavaScript, Property, Read-only, Reference, RegExp, Regular Expressions
The non-standard $1, $2, $3, $4, $5, $6, $7, $8, $9 properties are static and read-only properties of regular expressions that contain parenthesized substring matches.
557 RegExp.input ($_) JavaScript, Property, Reference, RegExp, Regular Expressions
The non-standard input property is a static property of regular expressions that contains the string against which a regular expression is matched. RegExp.$_ is an alias for this property.
558 RegExp.lastMatch ($&) JavaScript, Property, Read-only, Reference, RegExp, Regular Expressions
The non-standard lastMatch property is a static and read-only property of regular expressions that contains the last matched characters. RegExp.$& is an alias for this property.
559 RegExp.lastParen ($+) JavaScript, Property, Read-only, Reference, RegExp, Regular Expressions
The non-standard lastParen property is a static and read-only property of regular expressions that contains the last parenthesized substring match, if any. RegExp.$+ is an alias for this property.
560 RegExp.leftContext ($`) JavaScript, Property, Read-only, Reference, RegExp, Regular Expressions
The non-standard leftContext property is a static and read-only property of regular expressions that contains the substring preceding the most recent match. RegExp.$` is an alias for this property.
561 RegExp.prototype JavaScript, Property, Prototype, Reference, RegExp
The RegExp.prototype property represents the prototype object for the RegExp constructor.
562 RegExp.prototype.compile() Deprecated, JavaScript, Method, Prototype, Reference, RegExp, Regular Expressions
The deprecated compile() method is used to (re-)compile a regular expression during execution of a script. It is basically the same as the RegExp constructor.
563 RegExp.prototype.exec() JavaScript, Method, Prototype, Reference, RegExp, Regular Expressions
The exec() method executes a search for a match in a specified string. Returns a result array, or null.
564 RegExp.prototype.flags ECMAScript 2015, JavaScript, Property, Prototype, Reference, RegExp, Regular Expressions
The flags property returns a string consisting of the flags of the current regular expression object.
565 RegExp.prototype.global JavaScript, Property, Prototype, Reference, RegExp, Regular Expressions
The global property indicates whether or not the "g" flag is used with the regular expression. global is a read-only property of an individual regular expression instance.
566 RegExp.prototype.ignoreCase JavaScript, Property, Prototype, Reference, RegExp, Regular Expressions
The ignoreCase property indicates whether or not the "i" flag is used with the regular expression. ignoreCase is a read-only property of an individual regular expression instance.
567 RegExp.prototype.multiline JavaScript, Property, Prototype, Reference, RegExp, Regular Expressions
The multiline property indicates whether or not the "m" flag is used with the regular expression. multiline is a read-only property of an individual regular expression instance.
568 RegExp.prototype.source JavaScript, Property, Prototype, Reference, RegExp, Regular Expressions
The source property returns a String containing the source text of the regexp object, and it doesn't contain the two forward slashes on both sides and any flags.
569 RegExp.prototype.sticky ECMAScript 2015, JavaScript, Property, Prototype, Reference, RegExp, Regular Expressions
The sticky property reflects whether or not the search is sticky (searches in strings only from the index indicated by the lastIndex property of this regular expression). sticky is a read-only property of an individual regular expression object.
570 RegExp.prototype.test() JavaScript, Method, Prototype, Reference, RegExp, Regular Expressions
The test() method executes a search for a match between a regular expression and a specified string. Returns true or false.
571 RegExp.prototype.toSource() JavaScript, Method, Prototype, Reference, RegExp, Regular Expressions
The toSource() method returns a string representing the source code of the object.
572 RegExp.prototype.toString() JavaScript, Method, Prototype, Reference, RegExp, Regular Expressions
The toString() method returns a string representing the regular expression.
573 RegExp.prototype.unicode ECMAScript 2015, JavaScript, Property, Prototype, Reference, RegExp, Regular Expressions
The unicode property indicates whether or not the "u" flag is used with a regular expression. unicode is a read-only property of an individual regular expression instance.
574 RegExp.prototype[@@match]() JavaScript, Method, Prototype, Reference, RegExp, Regular Expressions
The [@@match]() method retrieves the matches when matching a string against a regular expression.
575 RegExp.prototype[@@replace]() JavaScript, Method, Prototype, Reference, RegExp, Regular Expressions
The [@@replace]() method replaces some or all matches of a this pattern in a string by a replacement, and returns the result of the replacement as a new string. The replacement can be a string or a function to be called for each match.
576 RegExp.prototype[@@search]() JavaScript, Method, Prototype, Reference, RegExp, Regular Expressions
The [@@search]() method executes a search for a match between a this regular expression and a string.
577 RegExp.prototype[@@split]() JavaScript, Method, Prototype, Reference, RegExp, Regular Expressions
The [@@split]() method splits a String object into an array of strings by separating the string into substrings.
578 RegExp.rightContext ($') JavaScript, Property, Read-only, Reference, RegExp, Regular Expressions
The non-standard rightContext property is a static and read-only property of regular expressions that contains the substring following the most recent match. RegExp.$' is an alias for this property.
579 get RegExp[@@species] JavaScript, Property, Prototype, Reference, RegExp, Regular Expressions
The RegExp[@@species] accessor property returns the RegExp constructor.
580 regexp.lastIndex JavaScript, Property, Reference, RegExp, Regular Expressions
The lastIndex is a read/write integer property of regular expression instances that specifies the index at which to start the next match.
581 Set ECMAScript 2015, Global Objects, JavaScript, Object, set
The Set object lets you store unique values of any type, whether primitive values or object references.
582 Set.prototype ECMAScript 2015, JavaScript, Property, set
The Set.prototype property represents the prototype for the Set constructor.
583 Set.prototype.add() ECMAScript 2015, JavaScript, Method, Prototype, set
The add() method appends a new element with a specified value to the end of a Set object.
584 Set.prototype.clear() ECMAScript 2015, JavaScript, Method, Prototype, set
The clear() method removes all elements from a Set object.
585 Set.prototype.delete() ECMAScript 2015, JavaScript, Method, Prototype, set
The delete() method removes the specified element from a Set object.
586 Set.prototype.entries() ECMAScript 2015, Iterator, JavaScript, Method, Prototype, set
The entries() method returns a new Iterator object that contains an array of [value, value] for each element in the Set object, in insertion order. For Set objects there is no key like in Map objects. However, to keep the API similar to the Map object, each entry has the same value for its key and value here, so that an array [value, value] is returned.
587 Set.prototype.forEach() ECMAScript 2015, JavaScript, Method, Prototype, set
The forEach() method executes a provided function once for each value in the Set object, in insertion order.
588 Set.prototype.has() ECMAScript 2015, JavaScript, Method, Prototype, set
The has() method returns a boolean indicating whether an element with the specified value exists in a Set object or not.
589 Set.prototype.size ECMAScript 2015, JavaScript, Property, Prototype, set
The size accessor property returns the number of elements in a Set object.
590 Set.prototype.values() ECMAScript 2015, Iterator, JavaScript, Method, Prototype, set
The values() method returns a new Iterator object that contains the values for each element in the Set object in insertion order.
591 Set.prototype[@@iterator]() ECMAScript 2015, Iterator, JavaScript, Method, Prototype, Reference, set
The initial value of the @@iterator property is the same function object as the initial value of the values property.
592 get Set[@@species] ECMAScript 2015, JavaScript, Property, set
The Set[@@species] accessor property returns the Set constructor.
593 SharedArrayBuffer Constructor, JavaScript, Shared Memory, SharedArrayBuffer, TypedArrays
The SharedArrayBuffer object is used to represent a generic, fixed-length raw binary data buffer, similar to the ArrayBuffer object, but in a way that they can be used to create views on shared memory. Unlike an ArrayBuffer, a SharedArrayBuffer cannot become detached.
594 SharedArrayBuffer.prototype JavaScript, Property, Shared Memory, SharedArrayBuffer, TypedArrays
The SharedArrayBuffer.prototype property represents the prototype for the SharedArrayBuffer object.
595 SharedArrayBuffer.prototype.byteLength JavaScript, Property, Shared Memory, SharedArrayBuffer, TypedArrays
The byteLength accessor property represents the length of an SharedArrayBuffer in bytes.
596 SharedArrayBuffer.prototype.slice() JavaScript, Method, Prototype, Shared Memory, SharedArrayBuffer, TypedArrays
The SharedArrayBuffer.prototype.slice() method returns a new SharedArrayBuffer whose contents are a copy of this SharedArrayBuffer's bytes from begin, inclusive, up to end, exclusive. If either begin or end is negative, it refers to an index from the end of the array, as opposed to from the beginning. This method has the same algorithm as Array.prototype.slice().
597 String ECMAScript 2015, JavaScript, Reference, String
The String global object is a constructor for strings or a sequence of characters.
598 String.fromCharCode() JavaScript, Method, Reference, String, Unicode
The static String.fromCharCode() method returns a string created from the specified sequence of UTF-16 code units.
599 String.fromCodePoint() ECMAScript 2015, JavaScript, Method, Reference, String
The static String.fromCodePoint() method returns a string created by using the specified sequence of code points.
600 String.prototype JavaScript, Property, Prototype, Reference, String
The String.prototype property represents the String prototype object.
601 String.prototype.anchor() Deprecated, HTML wrapper methods, JavaScript, Method, Prototype, Reference, String
The anchor() method creates an <a> HTML anchor element that is used as a hypertext target.
602 String.prototype.big() Deprecated, HTML wrapper methods, JavaScript, Method, Prototype, Reference, String
The big() method creates a <big> HTML element that causes a string to be displayed in a big font.
603 String.prototype.blink() Deprecated, HTML wrapper methods, JavaScript, Method, Prototype, Reference, String
The blink() method creates a <blink> HTML element that causes a string to blink.
604 String.prototype.bold() Deprecated, HTML wrapper methods, JavaScript, Method, Prototype, Reference, String
The bold() method creates a <b> HTML element that causes a string to be displayed as bold.
605 String.prototype.charAt() JavaScript, Method, Prototype, Reference, String
The String object's charAt() method returns a new string consisting of the single UTF-16 code unit located at the specified offset into the string.
606 String.prototype.charCodeAt() JavaScript, Method, Reference, String, Unicode
The charCodeAt() method returns an integer between 0 and 65535 representing the UTF-16 code unit at the given index.
607 String.prototype.codePointAt() ECMAScript 2015, JavaScript, Method, Prototype, Reference, String
The codePointAt() method returns a non-negative integer that is the Unicode code point value.
608 String.prototype.concat() JavaScript, Method, Prototype, Reference, String
The concat() method concatenates the string arguments to the calling string and returns a new string.
609 String.prototype.endsWith() JavaScript, Method, Prototype, Reference, String
The endsWith() method determines whether a string ends with the characters of a specified string, returning true or false as appropriate.
610 String.prototype.fixed() Deprecated, HTML wrapper methods, JavaScript, Method, Prototype, Reference, String
The fixed() method creates a <tt> HTML element that causes a string to be displayed in fixed-pitch font.
611 String.prototype.fontcolor() Deprecated, HTML wrapper methods, JavaScript, Method, Prototype, Reference, String
The fontcolor() method creates a <font> HTML element that causes a string to be displayed in the specified font color.
612 String.prototype.fontsize() Deprecated, HTML wrapper methods, JavaScript, Method, Prototype, Reference, String
The fontsize() method creates a <font> HTML element that causes a string to be displayed in the specified font size.
613 String.prototype.includes() JavaScript, Method, Prototype, Reference, String
The includes() method determines whether one string may be found within another string, returning true or false as appropriate.
614 String.prototype.indexOf() JavaScript, Method, Prototype, Reference, String
The indexOf() method returns the index within the calling String object of the first occurrence of the specified value, starting the search at fromIndex. Returns -1 if the value is not found.
615 String.prototype.italics() Deprecated, HTML wrapper methods, JavaScript, Method, Prototype, String
The italics() method creates an <i> HTML element that causes a string to be italic.
616 String.prototype.lastIndexOf() JavaScript, Method, Prototype, Reference, String
The lastIndexOf() method returns the index within the calling String object of the last occurrence of the specified value, searching backwards from fromIndex. Returns -1 if the value is not found.
617 String.prototype.link() Deprecated, HTML wrapper methods, JavaScript, Method, Prototype, Reference, String
The link() method creates a string representing the code for an <a> HTML element to be used as a hypertext link to another URL.
618 String.prototype.localeCompare() Internationalization, JavaScript, Method, Prototype, Reference, String
The localeCompare() method returns a number indicating whether a reference string comes before or after or is the same as the given string in sort order.
619 String.prototype.match() JavaScript, Method, Prototype, Reference, Regular Expressions, String
The match() method retrieves the matches when matching a string against a regular expression.
620 String.prototype.normalize() ECMAScript 2015, JavaScript, Method, Prototype, Reference, String, Unicode
The normalize() method returns the Unicode Normalization Form of a given string (if the value isn't a string, it will be converted to one first).
621 String.prototype.padEnd() JavaScript, Method, Reference, String
The padEnd() method pads the current string with a given string (repeated, if needed) so that the resulting string reaches a given length. The padding is applied from the end (right) of the current string.
622 String.prototype.padStart() JavaScript, Method, Reference, String
The padStart() method pads the current string with another string (multiple times, if needed) until the resulting string reaches the given length.
623 String.prototype.quote() JavaScript, Method, Obsolete, Prototype, Reference, String
The non-standard quote() method returns a copy of the string, replacing various special characters in the string with their escape sequences and wrapping the result in double-quotes (").
624 String.prototype.repeat() ECMAScript 2015, JavaScript, Method, Prototype, Reference, String
The repeat() method constructs and returns a new string which contains the specified number of copies of the string on which it was called, concatenated together.
625 String.prototype.replace() Expressions, JavaScript, Method, Prototype, Reference, Regular, String
The replace() method returns a new string with some or all matches of a pattern replaced by a replacement. The pattern can be a string or a RegExp, and the replacement can be a string or a function to be called for each match. If pattern is a string, only the first occurrence will be replaced.
626 String.prototype.search() JavaScript, Method, Prototype, Reference, Regular Expressions, String
The search() method executes a search for a match between a regular expression and this String object.
627 String.prototype.slice() JavaScript, Method, Prototype, Reference, String
The slice() method extracts a section of a string and returns it as a new string, without modifying the original string.
628 String.prototype.small() Deprecated, HTML wrapper methods, JavaScript, Method, Prototype, Reference, String
The small() method creates a <small> HTML element that causes a string to be displayed in a small font.
629 String.prototype.split() JavaScript, Method, Prototype, Reference, Regular Expressions, String
The split() method splits a String object into an array of strings by separating the string into substrings, using a specified separator string to determine where to make each split.
630 String.prototype.startsWith() ECMAScript 2015, JavaScript, Method, Prototype, Reference, String
The startsWith() method determines whether a string begins with the characters of a specified string, returning true or false as appropriate.
631 String.prototype.strike() Deprecated, HTML wrapper methods, JavaScript, Method, Prototype, String
The strike() method creates a <strike> HTML element that causes a string to be displayed as struck-out text.
632 String.prototype.sub() Deprecated, HTML wrapper methods, JavaScript, Method, Prototype, String
The sub() method creates a <sub> HTML element that causes a string to be displayed as subscript.
633 String.prototype.substr() Deprecated, JavaScript, Method, Prototype, Reference, String
The substr() method returns the part of a string between the start index and a number of characters after it.
634 String.prototype.substring() JavaScript, Method, Prototype, Reference, String
The substring() method returns the part of the string between the start and end indexes, or to the end of the string.
635 String.prototype.sup() Deprecated, HTML wrapper methods, JavaScript, Method, Prototype, Reference, String
The sup() method creates a <sup> HTML element that causes a string to be displayed as superscript.
636 String.prototype.toLocaleLowerCase() Internationalization, JavaScript, Method, Prototype, Reference, String
The toLocaleLowerCase() method returns the calling string value converted to lower case, according to any locale-specific case mappings.
637 String.prototype.toLocaleUpperCase() Internationalization, JavaScript, Method, Prototype, Reference, String
The toLocaleUpperCase() method returns the calling string value converted to upper case, according to any locale-specific case mappings.
638 String.prototype.toLowerCase() JavaScript, Method, Prototype, Reference, String
The toLowerCase() method returns the calling string value converted to lower case.
639 String.prototype.toSource() JavaScript, Method, Non-standard, Prototype, Reference, String
The toSource() method returns a string representing the source code of the object.
640 String.prototype.toString() JavaScript, Method, Prototype, Reference, String
The toString() method returns a string representing the specified object.
641 String.prototype.toUpperCase() JavaScript, Method, Prototype, Reference, String
The toUpperCase() method returns the calling string value converted to uppercase (the value will be converted to a string if it isn't one).
642 String.prototype.trim() ECMAScript 5, JavaScript, Method, Prototype, Reference, String
The trim() method removes whitespace from both ends of a string. Whitespace in this context is all the whitespace characters (space, tab, no-break space, etc.) and all the line terminator characters (LF, CR, etc.).
643 String.prototype.trimEnd() JavaScript, Method, Prototype, Reference, String
The trimEnd() method removes whitespace from the end of a string. trimRight() is an alias of this method.
644 String.prototype.trimStart() JavaScript, Method, Prototype, Reference, String
The trimStart() method removes whitespace from the beginning of a string. trimLeft() is an alias of this method.
645 String.prototype.valueOf() JavaScript, Method, Prototype, Reference, String
The valueOf() method returns the primitive value of a String object.
646 String.prototype[@@iterator]() ECMAScript 2015, Iterator, JavaScript, Method, Prototype, Reference, String
The [@@iterator]() method returns a new Iterator object that iterates over the code points of a String value, returning each code point as a String value.
647 String.raw() ECMAScript 2015, JavaScript, Method, Reference, String
The static String.raw() method is a tag function of template literals, similar to the r prefix in Python or the @ prefix in C# for string literals (yet there is a difference: see explanations in this issue). It's used to get the raw string form of template strings, that is, substitutions (e.g. ${foo}) are processed, but escapes (e.g. \n) are not.
648 string.length JavaScript, Property, Prototype, Reference, String, String Length, length
The length property of a String object indicates the length of a string, in UTF-16 code units.
649 Symbol ECMAScript 2015, JavaScript, Symbol
The Symbol() function returns a value of type symbol, has static properties that expose several members of built-in objects, has static methods that expose the global symbol registry, and resembles a built-in object class but is incomplete as a constructor because it does not support the syntax "new Symbol()".
650 Symbol.for() ECMAScript 2015, JavaScript, Method, Symbol
The Symbol.for(key) method searches for existing symbols in a runtime-wide symbol registry with the given key and returns it if found. Otherwise a new symbol gets created in the global symbol registry with this key.
651 Symbol.hasInstance ECMAScript 2015, JavaScript, Property, Reference, Symbol
The Symbol.hasInstance well-known symbol is used to determine if a constructor object recognizes an object as its instance. The instanceof operator's behavior can be customized by this symbol.
652 Symbol.isConcatSpreadable ECMAScript 2015, JavaScript, Property, Symbol
The Symbol.isConcatSpreadable well-known symbol is used to configure if an object should be flattened to its array elements when using the Array.prototype.concat() method.
653 Symbol.iterator ECMAScript 2015, JavaScript, Property, Symbol
The Symbol.iterator well-known symbol specifies the default iterator for an object. Used by for...of.
654 Symbol.keyFor() ECMAScript 2015, JavaScript, Method, Symbol
The Symbol.keyFor(sym) method retrieves a shared symbol key from the global symbol registry for the given symbol.
655 Symbol.match ECMAScript 2015, JavaScript, Property, Symbol
The Symbol.match well-known symbol specifies the matching of a regular expression against a string. This function is called by the String.prototype.match() method.
656 Symbol.prototype JavaScript, Property, Symbol
The Symbol.prototype property represents the prototype for the Symbol constructor.
657 Symbol.prototype.description JavaScript, Property, Prototype, Symbol
The read-only description property is a string returning the optional description of Symbol objects.
658 Symbol.prototype.toSource() JavaScript, Method, Prototype, Symbol
The toSource() method returns a string representing the source code of the object.
659 Symbol.prototype.toString() ECMAScript 2015, JavaScript, Method, Prototype, Symbol
The toString() method returns a string representing the specified Symbol object.
660 Symbol.prototype.valueOf() ECMAScript 2015, JavaScript, Method, Prototype, Symbol
The valueOf() method returns the primitive value of a Symbol object.
661 Symbol.prototype[@@toPrimitive] ECMAScript 2015, JavaScript, Method, Prototype, Symbol
The [@@toPrimitive]() method converts a Symbol object to a primitive value.
662 Symbol.replace ECMAScript 2015, JavaScript, Property, Symbol
The Symbol.replace well-known symbol specifies the method that replaces matched substrings of a string. This function is called by the String.prototype.replace() method.
663 Symbol.search ECMAScript 2015, JavaScript, Property, Symbol
The Symbol.search well-known symbol specifies the method that returns the index within a string that matches the regular expression. This function is called by the String.prototype.search() method.
664 Symbol.species ECMAScript 2015, JavaScript, Property, Symbol
The well-known symbol Symbol.species specifies a function-valued property that the constructor function uses to create derived objects.
665 Symbol.split ECMAScript 2015, JavaScript, Property, Symbol
The Symbol.split well-known symbol specifies the method that splits a string at the indices that match a regular expression. This function is called by the String.prototype.split() method.
666 Symbol.toPrimitive ECMAScript 2015, JavaScript, Property, Symbol
The Symbol.toPrimitive is a symbol that specifies a function valued property that is called to convert an object to a corresponding primitive value.
667 Symbol.toStringTag ECMAScript 2015, JavaScript, Property, Reference, Symbol
The Symbol.toStringTag well-known symbol is a string valued property that is used in the creation of the default string description of an object. It is accessed internally by the Object.prototype.toString() method.
668 Symbol.unscopables ECMAScript 2015, JavaScript, Property, Symbol
The Symbol.unscopables well-known symbol is used to specify an object value of whose own and inherited property names are excluded from the with environment bindings of the associated object.
669 SyntaxError Error, JavaScript, Object, Reference, SyntaxError
The SyntaxError object represents an error when trying to interpret syntactically invalid code.
670 SyntaxError.prototype Error, JavaScript, Property, Prototype, SyntaxError
The SyntaxError.prototype property represents the prototype for the SyntaxError constructor.
671 TypeError Error, JavaScript, Object, Reference, TypeError
The TypeError object represents an error when a value is not of the expected type.
672 TypeError.prototype Error, JavaScript, Property, Prototype, TypeError
The TypeError.prototype property represents the prototype for the TypeError constructor.
673 TypedArray JavaScript, TypedArray, TypedArrays
A TypedArray object describes an array-like view of an underlying binary data buffer. There is no global property named TypedArray, nor is there a directly visible TypedArray constructor.  Instead, there are a number of different global properties, whose values are typed array constructors for specific element types, listed below. On the following pages you will find common properties and methods that can be used with any typed array containing elements of any type.
674 TypedArray.BYTES_PER_ELEMENT JavaScript, Property, TypedArray, TypedArrays
The TypedArray.BYTES_PER_ELEMENT property represents the size in bytes of each element in an typed array.
675 TypedArray.from() ECMAScript 2015, JavaScript, Method, TypedArray, TypedArrays
The TypedArray.from() method creates a new typed array from an array-like or iterable object. This method is nearly the same as Array.from().
676 TypedArray.name JavaScript, Property, TypedArray, TypedArrays
The TypedArray.name property represents a string value of the typed array constructor name.
677 TypedArray.of() ECMAScript 2015, JavaScript, Method, TypedArray, TypedArrays
The TypedArray.of() method creates a new typed array with a variable number of arguments. This method is nearly the same as Array.of().
678 TypedArray.prototype JavaScript, Property, TypedArray, TypedArrays
The TypedArray.prototype property represents the prototype for TypedArray constructors.
679 TypedArray.prototype.buffer JavaScript, Property, Prototype, TypedArray, TypedArrays
The buffer accessor property represents the ArrayBuffer referenced by a TypedArray at construction time.
680 TypedArray.prototype.byteLength JavaScript, Property, Prototype, TypedArray, TypedArrays
The byteLength accessor property represents the length (in bytes) of a typed array.
681 TypedArray.prototype.byteOffset JavaScript, Property, Prototype, TypedArray, TypedArrays
The byteOffset accessor property represents the offset (in bytes) of a typed array from the start of its ArrayBuffer.
682 TypedArray.prototype.copyWithin() JavaScript, Method, Prototype, TypedArray, TypedArrays
The copyWithin() method copies the sequence of array elements within the array to the position starting at target. The copy is taken from the index positions of the second and third arguments start and end. The end argument is optional and defaults to the length of the array. This method has the same algorithm as Array.prototype.copyWithin. TypedArray is one of the typed array types here.
683 TypedArray.prototype.entries() ECMAScript 2015, Iterator, JavaScript, Method, Prototype, Reference, TypedArray, TypedArrays
The entries() method returns a new Array Iterator object that contains the key/value pairs for each index in the array.
684 TypedArray.prototype.every() ECMAScript 2015, JavaScript, Method, Prototype, TypedArray, TypedArrays
The every() method tests whether all elements in the typed array pass the test implemented by the provided function. This method has the same algorithm as Array.prototype.every(). TypedArray is one of the typed array types here.
685 TypedArray.prototype.fill() ECMAScript 2015, JavaScript, Method, Prototype, TypedArray, TypedArrays
The fill() method fills all the elements of a typed array from a start index to an end index with a static value. This method has the same algorithm as Array.prototype.fill(). TypedArray is one of the typed array types here.
686 TypedArray.prototype.filter() ECMAScript 2015, JavaScript, Method, Prototype, TypedArray, TypedArrays
The filter() method creates a new typed array with all elements that pass the test implemented by the provided function. This method has the same algorithm as Array.prototype.filter(). TypedArray is one of the typed array types here.
687 TypedArray.prototype.find() ECMAScript 2015, JavaScript, Method, Prototype, Reference, TypedArray, TypedArrays
The find() method returns a value in the typed array, if an element satisfies the provided testing function. Otherwise undefined is returned. TypedArray is one of the typed array types here.
688 TypedArray.prototype.findIndex() ECMAScript 2015, JavaScript, Method, Prototype, Reference, TypedArray, TypedArrays
The findIndex() method returns an index in the typed array, if an element in the typed array satisfies the provided testing function. Otherwise -1 is returned.
689 TypedArray.prototype.forEach() ECMAScript 2015, JavaScript, Method, Prototype, Reference, TypedArray, TypedArrays
The forEach() method executes a provided function once per array element. This method has the same algorithm as Array.prototype.forEach(). TypedArray is one of the typed array types here.
690 TypedArray.prototype.includes() ECMAScript 2016, JavaScript, Method, Prototype, TypedArray, TypedArrays
The includes() method determines whether a typed array includes a certain element, returning true or false as appropriate. This method has the same algorithm as Array.prototype.includes(). TypedArray is one of the typed array types here.
691 TypedArray.prototype.indexOf() ECMAScript 2015, JavaScript, Method, Prototype, TypedArray, TypedArrays
The indexOf() method returns the first index at which a given element can be found in the typed array, or -1 if it is not present. This method has the same algorithm as Array.prototype.indexOf(). TypedArray is one of the typed array types here.
692 TypedArray.prototype.join() ECMAScript 2015, JavaScript, Method, Prototype, TypedArray, TypedArrays
The join() method joins all elements of an array into a string. This method has the same algorithm as Array.prototype.join(). TypedArray is one of the typed array types here.
693 TypedArray.prototype.keys() ECMAScript 2015, Iterator, JavaScript, Method, Prototype, Reference, TypedArray, TypedArrays
The keys() method returns a new Array Iterator object that contains the keys for each index in the array.
694 TypedArray.prototype.lastIndexOf() ECMAScript 2015, JavaScript, Method, Prototype, TypedArray, TypedArrays
The lastIndexOf() method returns the last index at which a given element can be found in the typed array, or -1 if it is not present. The typed array is searched backwards, starting at fromIndex. This method has the same algorithm as Array.prototype.lastIndexOf(). TypedArray is one of the typed array types here.
695 TypedArray.prototype.length JavaScript, Property, Prototype, TypedArray, TypedArrays
The length accessor property represents the length (in elements) of a typed array.
696 TypedArray.prototype.map() ECMAScript 2015, JavaScript, Method, Prototype, TypedArray, TypedArrays
The map() method creates a new typed array with the results of calling a provided function on every element in this typed array. This method has the same algorithm as Array.prototype.map(). TypedArray is one of the typed array types here.
697 TypedArray.prototype.move() JavaScript, Method, Obsolete, Prototype, TypedArray
The move() method used to copy the sequence of array elements within the array to the position starting at target. However, this non-standard method has been replaced with the standard TypedArray.prototype.copyWithin() method. TypedArray is one of the typed array types here.
698 TypedArray.prototype.reduce() JavaScript, Method, Prototype, Reference, TypedArray, TypedArrays
The reduce() method applies a function against an accumulator and each value of the typed array (from left-to-right) has to reduce it to a single value. This method has the same algorithm as Array.prototype.reduce(). TypedArray is one of the typed array types here.
699 TypedArray.prototype.reduceRight() JavaScript, Method, Prototype, Reference, TypedArray, TypedArrays
The reduceRight() method applies a function against an accumulator and each value of the typed array (from right-to-left) has to reduce it to a single value. This method has the same algorithm as Array.prototype.reduceRight(). TypedArray is one of the typed array types here.
700 TypedArray.prototype.reverse() ECMAScript 2015, JavaScript, Method, Prototype, TypedArray, TypedArrays
The reverse() method reverses a typed array in place. The first typed array element becomes the last and the last becomes the first. This method has the same algorithm as Array.prototype.reverse(). TypedArray is one of the typed array types here.
701 TypedArray.prototype.set() JavaScript, Method, Prototype, TypedArray, TypedArrays
The set() method stores multiple values in the typed array, reading input values from a specified array.
702 TypedArray.prototype.slice() ECMAScript 2015, JavaScript, Method, Prototype, TypedArray, TypedArrays
The slice() method returns a shallow copy of a portion of a typed array into a new typed array object. This method has the same algorithm as Array.prototype.slice(). TypedArray is one of the typed array types here.
703 TypedArray.prototype.some() ECMAScript 2015, JavaScript, Method, Prototype, TypedArray, TypedArrays
The some() method tests whether some element in the typed array passes the test implemented by the provided function. This method has the same algorithm as Array.prototype.some(). TypedArray is one of the typed array types here.
704 TypedArray.prototype.sort() ECMAScript 2015, JavaScript, Method, Prototype, TypedArray, TypedArrays
The sort() method sorts the elements of a typed array numerically in place and returns the typed array. This method has the same algorithm as Array.prototype.sort(), except that sorts the values numerically instead of as strings. TypedArray is one of the typed array types here.
705 TypedArray.prototype.subarray() JavaScript, Method, Prototype, TypedArray, TypedArrays
The subarray() method returns a new TypedArray on the same ArrayBuffer store and with the same element types as for this TypedArray object. The begin offset is inclusive and the end offset is exclusive. TypedArray is one of the typed array types.
706 TypedArray.prototype.toLocaleString() ECMAScript 2015, JavaScript, Method, Prototype, TypedArray, TypedArrays
The toLocaleString() method returns a string representing the elements of the typed array. The elements are converted to strings and are separated by a locale-specific string (such as a comma “,”). This method has the same algorithm as Array.prototype.toLocaleString() and, as the typed array elements are numbers, the same algorithm as Number.prototype.toLocaleString() applies for each element. TypedArray is one of the typed array types here.
707 TypedArray.prototype.toString() ECMAScript 2015, JavaScript, Method, Prototype, TypedArray
The toString() method returns a string representing the specified array and its elements. This method has the same algorithm as Array.prototype.toString(). TypedArray is one of the typed array types here.
708 TypedArray.prototype.values() ECMAScript 2015, Iterator, JavaScript, Method, Prototype, TypedArray, TypedArrays
The values() method returns a new Array Iterator object that contains the values for each index in the array.
709 TypedArray.prototype[@@iterator]() Iterator, JavaScript, Method, Prototype, Reference, TypedArray, TypedArrays
The initial value of the @@iterator property is the same function object as the initial value of the values property.
710 get TypedArray[@@species] JavaScript, Property, Prototype, TypedArray, TypedArrays
The TypedArray[@@species] accessor property returns the constructor of a typed array.
711 URIError Error, JavaScript, Object, Reference, URIError
The URIError object represents an error when a global URI handling function was used in a wrong way.
712 URIError.prototype Error, JavaScript, Property, Prototype, URIError
The URIError.prototype property represents the prototype for the URIError constructor.
713 Uint16Array Constructor, JavaScript, TypedArray, TypedArrays, Uint16Array
The Uint16Array typed array represents an array of 16-bit unsigned integers in the platform byte order. If control over byte order is needed, use DataView instead. The contents are initialized to 0. Once established, you can reference elements in the array using the object's methods, or using standard array index syntax (that is, using bracket notation).
714 Uint32Array Constructor, JavaScript, TypedArray, TypedArrays
The Uint32Array typed array represents an array of 32-bit unsigned integers in the platform byte order. If control over byte order is needed, use DataView instead. The contents are initialized to 0. Once established, you can reference elements in the array using the object's methods, or using standard array index syntax (that is, using bracket notation).
715 Uint8Array Constructor, JavaScript, TypedArray, TypedArrays, Uint8Array
The Uint8Array typed array represents an array of 8-bit unsigned integers. The contents are initialized to 0. Once established, you can reference elements in the array using the object's methods, or using standard array index syntax (that is, using bracket notation).
716 Uint8ClampedArray Constructor, JavaScript, TypedArray, TypedArrays, Uint8ClampedArray
The Uint8ClampedArray typed array represents an array of 8-bit unsigned integers clamped to 0-255; if you specified a value that is out of the range of [0,255], 0 or 255 will be set instead; if you specify a non-integer, the nearest integer will be set. The contents are initialized to 0. Once established, you can reference elements in the array using the object's methods, or using standard array index syntax (that is, using bracket notation).
717 WeakMap ECMAScript 2015, JavaScript, Reference, WeakMap
The WeakMap object is a collection of key/value pairs in which the keys are weakly referenced.  The keys must be objects and the values can be arbitrary values.
718 WeakMap.prototype ECMAScript 2015, JavaScript, Property, WeakMap
The WeakMap.prototype property represents the prototype for the WeakMap constructor.
719 WeakMap.prototype.clear() JavaScript, Method, Obsolete, Prototype, WeakMap
The clear() method used to remove all elements from a WeakMap object, but is no longer part of ECMAScript and its implementations.
720 WeakMap.prototype.delete() ECMAScript 2015, JavaScript, Method, Prototype, WeakMap
The delete() method removes the specified element from a WeakMap object.
721 WeakMap.prototype.get() ECMAScript 2015, JavaScript, Method, Prototype, WeakMap
The get() method returns a specified element from a WeakMap object.
722 WeakMap.prototype.has() ECMAScript 2015, JavaScript, Method, Prototype, WeakMap
The has() method returns a boolean indicating whether an element with the specified key exists in the WeakMap object or not.
723 WeakMap.prototype.set() ECMAScript 2015, JavaScript, Method, Prototype, WeakMap
The set() method adds a new element with a specified key and value to a WeakMap object.
724 WeakSet ECMAScript 2015, JavaScript, WeakSet
The WeakSet object lets you store weakly held objects in a collection.
725 WeakSet.prototype ECMAScript 2015, JavaScript, Property, WeakSet
The WeakSet.prototype property represents the prototype for the WeakSet constructor.
726 WeakSet.prototype.add() ECMAScript 2015, JavaScript, Method, Prototype, WeakSet
The add() method appends a new object to the end of a WeakSet object.
727 WeakSet.prototype.clear() JavaScript, Method, Obsolete, Prototype, WeakSet
The clear() method used to remove all elements from a WeakSet object, but is no longer part of ECMAScript and its implementations.
728 WeakSet.prototype.delete() ECMAScript 2015, JavaScript, Method, Prototype, WeakSet
The delete() method removes the specified element from a WeakSet object.
729 WeakSet.prototype.has() ECMAScript 2015, JavaScript, Method, Prototype, WeakSet
The has() method returns a boolean indicating whether an object exists in a WeakSet or not.
730 WebAssembly API, JavaScript, Object, Reference, WebAssembly
The WebAssembly JavaScript object acts as the namespace for all WebAssembly-related functionality.
731 WebAssembly.CompileError() API, CompileError, Constructor, Error, JavaScript, NativeError, Reference, WebAssembly
The WebAssembly.CompileError() constructor creates a new WebAssembly CompileError object, which indicates an error during WebAssembly decoding or validation.
732 WebAssembly.Global API, Constructor, JavaScript, Reference, WebAssembly, global
A WebAssembly.Global object represents a global variable instance, accessible from both JavaScript and importable/exportable across one or more WebAssembly.Module instances. This allows dynamic linking of multiple modules.
733 WebAssembly.Global.prototype JavaScript, Property, Prototype, WebAssembly, global
The WebAssembly.Global.prototype property represents the prototype for the WebAssembly.Global() constructor.
734 WebAssembly.Instance API, Constructor, JavaScript, Reference, WebAssembly, instance
A WebAssembly.Instance object is a stateful, executable instance of a WebAssembly.ModuleInstance objects contain all the Exported WebAssembly functions that allow calling into WebAssembly code from JavaScript.
735 WebAssembly.Instance.prototype JavaScript, Property, Prototype, WebAssembly, instance
The WebAssembly.Instance.prototype property represents the prototype for the WebAssembly.Instance() constructor.
736 WebAssembly.Instance.prototype.exports API, JavaScript, Property, Reference, WebAssembly, exports, instance
The exports readonly property of the WebAssembly.Instance object prototype returns an object containing as its members all the functions exported from the WebAssembly module instance, to allow them to be accessed and used by JavaScript.
737 WebAssembly.LinkError() API, Constructor, JavaScript, LinkError, Reference, WebAssembly
The WebAssembly.LinkError() constructor creates a new WebAssembly LinkError object, which indicates an error during module instantiation (besides traps from the start function).
738 WebAssembly.Memory() API, Constructor, JavaScript, Object, Reference, WebAssembly, memory
The WebAssembly.Memory() constructor creates a new Memory object which is a resizable ArrayBuffer that holds the raw bytes of memory accessed by a WebAssembly Instance.
739 WebAssembly.Memory.prototype JavaScript, Property, Prototype, WebAssembly, memory
The WebAssembly.Memory.prototype property represents the prototype for the WebAssembly.Memory() constructor.
740 WebAssembly.Memory.prototype.buffer API, Buffer, JavaScript, Property, Reference, WebAssembly, memory
The buffer prototype property of the Memory object returns the buffer contained in the memory.
741 WebAssembly.Memory.prototype.grow() API, JavaScript, Method, Reference, WebAssembly, grow, memory
The grow() protoype method of the Memory object increases the size of the memory instance by a specified number of WebAssembly pages.
742 WebAssembly.Module API, Constructor, JavaScript, Module, Reference, WebAssembly
All Module instances inherit from the Module() constructor's prototype object — this can be modified to affect all Module instances.
743 WebAssembly.Module.customSections() API, Constructor, JavaScript, Method, Module, Object, Reference, WebAssembly, customSections
The WebAssembly.customSections() function returns a copy of the contents of all custom sections in the given module with the given string name.
744 WebAssembly.Module.exports() API, Constructor, JavaScript, Method, Module, Object, Reference, WebAssembly, exports
The WebAssembly.exports() function returns an array containing descriptions of all the declared exports of the given Module.
745 WebAssembly.Module.imports() API, Constructor, JavaScript, Method, Module, Object, Reference, WebAssembly, imports
The WebAssembly.imports() function returns an array containing descriptions of all the declared imports of the given Module.
746 WebAssembly.Module.prototype JavaScript, Module, Property, Prototype, WebAssembly
The WebAssembly.Module.prototype property represents the prototype for the WebAssembly.Module() constructor.
747 WebAssembly.RuntimeError() API, Constructor, JavaScript, Reference, RuntimeError, WebAssembly
The WebAssembly.RuntimeError() constructor creates a new WebAssembly RuntimeError object — the type that is thrown whenever WebAssembly specifies a trap.
748 WebAssembly.Table() API, Constructor, JavaScript, Object, Reference, WebAssembly, table
The WebAssembly.Table() constructor creates a new Table object of the given size and element type.
749 WebAssembly.Table.prototype JavaScript, Property, Prototype, WebAssembly, table
The WebAssembly.Table.prototype property represents the prototype for the WebAssembly.Table() constructor.
750 WebAssembly.Table.prototype.get() API, JavaScript, Method, Reference, WebAssembly, get, table
The get() prototype method of the WebAssembly.Table() object retrieves a function reference stored at a given index.
751 WebAssembly.Table.prototype.grow() API, JavaScript, Method, Reference, WebAssembly, grow, table
The grow() prototype method of the WebAssembly.Table object increases the size of the Table instance by a specified number of elements.
752 WebAssembly.Table.prototype.length API, JavaScript, Property, Reference, WebAssembly, length, table
The length prototype property of the WebAssembly.Table object returns the length of the table, i.e. the number of elements in the table.
753 WebAssembly.Table.prototype.set() API, JavaScript, Method, Reference, WebAssembly, set, table
The set() prototype method of the WebAssembly.Table object mutates a reference stored at a given index to a different value.
754 WebAssembly.compile() API, JavaScript, Method, Object, Reference, WebAssembly, compile
The WebAssembly.compile() function compiles a WebAssembly.Module from WebAssembly binary code.  This function is useful if it is necessary to a compile a module before it can be instantiated (otherwise, the WebAssembly.instantiate() function should be used).
755 WebAssembly.compileStreaming() API, Experimental, JavaScript, Method, Object, Reference, WebAssembly, compile, compileStreaming, streaming
The WebAssembly.compileStreaming() function compiles a WebAssembly.Module directly from a streamed underlying source.  This function is useful if it is necessary to a compile a module before it can be instantiated (otherwise, the WebAssembly.instantiateStreaming() function should be used).
756 WebAssembly.instantiate() API, JavaScript, Method, Object, Reference, WebAssembly, instantiate
The WebAssembly.instantiate() function allows you to compile and instantiate WebAssembly code.  This function has two overloads:
757 WebAssembly.instantiateStreaming() API, JavaScript, Method, Object, Reference, WebAssembly, instantiate, instantiateStreaming, streaming
The WebAssembly.instantiateStreaming() function compiles and instantiates a WebAssembly module directly from a streamed underlying source. This is the most efficient, optimized way to load wasm code.
758 WebAssembly.validate() API, JavaScript, Method, Object, Reference, WebAssembly, validate
The WebAssembly.validate() function validates a given typed array of WebAssembly binary code, returning whether the bytes form a valid wasm module (true) or not (false).
759 decodeURI() JavaScript
The decodeURI() function decodes a Uniform Resource Identifier (URI) previously created by encodeURI or by a similar routine.
760 decodeURIComponent() JavaScript
The decodeURIComponent() function decodes a Uniform Resource Identifier (URI) component previously created by encodeURIComponent or by a similar routine.
761 encodeURI() JavaScript, URI
The encodeURI() function encodes a Uniform Resource Identifier (URI) by replacing each instance of certain characters by one, two, three, or four escape sequences representing the UTF-8 encoding of the character (will only be four escape sequences for characters composed of two "surrogate" characters).
762 encodeURIComponent() JavaScript, URI
The encodeURIComponent() function encodes a Uniform Resource Identifier (URI) component by replacing each instance of certain characters by one, two, three, or four escape sequences representing the UTF-8 encoding of the character (will only be four escape sequences for characters composed of two "surrogate" characters).
763 escape() Deprecated, JavaScript
The escape() function computes a new string in which certain characters have been replaced by a hexadecimal escape sequence.
764 eval() JavaScript, eval
The eval() function evaluates JavaScript code represented as a string.
765 isFinite() JavaScript
The global isFinite() function determines whether the passed value is a finite number. If  needed, the parameter is first converted to a number.
766 isNaN() JavaScript, Method
The isNaN() function determines whether a value is NaN or not. Note: coercion inside the isNaN function has interesting rules; you may alternatively want to use Number.isNaN(), as defined in ECMAScript 2015.
767 null JavaScript, Literal, Primitive
The value null represents the intentional absence of any object value. It is one of JavaScript's primitive values.
768 parseFloat() JavaScript
The parseFloat() function parses an argument and returns a floating point number.
769 parseInt() JavaScript
The parseInt() function parses a string argument and returns an integer of the specified radix (the base in mathematical numeral systems).
770 undefined JavaScript
The global undefined property represents the primitive value undefined. It is one of JavaScript's primitive types.
771 unescape() Deprecated, JavaScript
The unescape() function computes a new string in which hexadecimal escape sequences are replaced with the character that it represents. The escape sequences might be introduced by a function like escape. Usually, decodeURI or decodeURIComponent are preferred over unescape.
772 uneval() JavaScript
The uneval() function creates a string representation of the source code of an Object.
773 Statements and declarations JavaScript, Reference, statements
JavaScript applications consist of statements with an appropriate syntax. A single statement may span multiple lines. Multiple statements may occur on a single line if each statement is separated by a semicolon. This isn't a keyword, but a group of keywords.
774 Legacy generator function JavaScript, Legacy Iterator, Non-standard, Obsolete, Reference
The legacy generator function statement declares legacy generator functions with the specified parameters.
775 async function Example, Function, JavaScript, Statement
The async function declaration defines an asynchronous function, which returns an AsyncFunction object.
776 block JavaScript, Reference, Statement
A block statement (or compound statement in other languages) is used to group zero or more statements. The block is delimited by a pair of curly brackets and may optionally be labelled:
777 break JavaScript, Statement
The break statement terminates the current loop, switch, or label statement and transfers program control to the statement following the terminated statement.
778 class Classes, Declaration, ECMAScript 2015, JavaScript, Reference, Statement
The class declaration creates a new class with a given name using prototype-based inheritance.
779 const ECMAScript 2015, JavaScript, Reference, Statement, constants
The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.
780 continue JavaScript, Statement
The continue statement terminates execution of the statements in the current iteration of the current or labeled loop, and continues execution of the loop with the next iteration.
781 debugger JavaScript, Statement
The debugger statement invokes any available debugging functionality, such as setting a breakpoint. If no debugging functionality is available, this statement has no effect.
782 default JavaScript, Keyword
The default keyword can be used in two situations in JavaScript: within a switch statement, or with an export statement.
783 do...while JavaScript, Statement
The do...while statement creates a loop that executes a specified statement until the test condition evaluates to false. The condition is evaluated after executing the statement, resulting in the specified statement executing at least once.
784 empty JavaScript, Statement
An empty statement is used to provide no statement, although the JavaScript syntax would expect one.
785 export ECMAScript 2015, JavaScript, Modules, Statement, export
The export statement is used when creating JavaScript modules to export functions, objects, or primitive values from the module so they can be used by other programs with the import statement.
786 for JavaScript, Loop, Reference, Statement, for
The for statement creates a loop that consists of three optional expressions, enclosed in parentheses and separated by semicolons, followed by a statement (usually a block statement) to be executed in the loop.
787 for each...in Deprecated, E4X, JavaScript, Obsolete, Statement
The for each...in statement iterates a specified variable over all values of object's properties. For each distinct property, a specified statement is executed.
788 for...in JavaScript, Statement
The for...in statement iterates over all non-Symbol, enumerable properties of an object.
789 for...of ECMAScript 2015, JavaScript, Reference, Statement
The for...of statement creates a loop iterating over iterable objects, including: built-in String, ArrayArray-like objects (e.g., arguments or NodeList), TypedArray, Map, Set, and user-defined iterables. It invokes a custom iteration hook with statements to be executed for the value of each distinct property of the object.
790 function declaration Function, JavaScript, Statement
The function declaration (function statement) defines a function with the specified parameters.
791 function* ECMAScript 2015, Function, Iterator, JavaScript, Statement
The function* declaration (function keyword followed by an asterisk) defines a generator function, which returns a Generator object.
792 if...else JavaScript, Statement
The if statement executes a statement if a specified condition is truthy. If the condition is falsy, another statement can be executed.
793 import ECMAScript 2015, JavaScript, Modules, Reference, Statement, dynamic import, import
The import statement is used to import bindings which are exported by another module. Imported modules are in strict mode whether you declare them as such or not. The import statement cannot be used in embedded scripts unless such script has a type="module".
794 import.meta JavaScript, Modules, Reference
The import.meta object is a meta-property exposing context-specific meta data to a JavaScript module. It contains information about the module, like the module's URL.
795 label JavaScript, Statement
The labeled statement can be used with break or continue statements. It is prefixing a statement with an identifier which you can refer to.
796 let ECMAScript 2015, JavaScript, Statement, Variable declaration, Variables, let
The let statement declares a block scope local variable, optionally initializing it to a value.
797 return JavaScript, Statement
The return statement ends function execution and specifies a value to be returned to the function caller.
798 switch JavaScript, Reference, Statement, Web
The switch statement evaluates an expression, matching the expression's value to a case clause, and executes statements associated with that case, as well as statements in cases that follow the matching case.
799 throw JavaScript, Statement
The throw statement throws a user-defined exception. Execution of the current function will stop (the statements after throw won't be executed), and control will be passed to the first catch block in the call stack. If no catch block exists among caller functions, the program will terminate.
800 try...catch Error, Exception, JavaScript, Statement
The try...catch statement marks a block of statements to try, and specifies a response, should an exception be thrown.
801 var JavaScript, Statement
The var statement declares a variable, optionally initializing it to a value.
802 while JavaScript, Statement
The while statement creates a loop that executes a specified statement as long as the test condition evaluates to true. The condition is evaluated before executing the statement.
803 with Deprecated, JavaScript, Statement
The with statement extends the scope chain for a statement.
804 Strict mode ECMAScript 5, JavaScript, Strict Mode
ECMAScript 5's strict mode is a way to opt in to a restricted variant of JavaScript, thereby implicitly opting-out of "sloppy mode". Strict mode isn't just a subset: it intentionally has different semantics from normal code. Browsers not supporting strict mode will run strict mode code with different behavior from browsers that do, so don't rely on strict mode without feature-testing for support for the relevant aspects of strict mode. Strict mode code and non-strict mode code can coexist, so scripts can opt into strict mode incrementally.
805 Transitioning to strict mode Advanced, JavaScript
ECMAScript 5 introduced strict mode which is now implemented in all major browsers (including IE10). While making web browsers interpret code as strict is easy (just add 'use strict'; at the top of your source code), transitioning an existing code base to strict mode requires a bit more work.
806 Template literals (Template strings) ECMAScript 2015, Guide, JavaScript, String, Template Strings, Template literals, Template string, strings
Template literals are string literals allowing embedded expressions. You can use multi-line strings and string interpolation features with them. They were called "template strings" in prior editions of the ES2015 specification.
807 Trailing commas Comma, ECMAScript2017, ECMAScript5, JavaScript, Syntax, Trailing comma
Trailing commas (sometimes called "final commas") can be useful when adding new elements, parameters, or properties to JavaScript code. If you want to add a new property, you can simply add a new line without modifying the previously last line if that line already uses a trailing comma. This makes version-control diffs cleaner and editing code might be less troublesome.
808 JavaScript shells Extensions, JavaScript, Tools
A JavaScript shell allows you to quickly test snippets of JavaScript code without having to reload a web page. They are extremely useful for developing and debugging code.
809 JavaScript technologies overview Beginner, DOM, JavaScript
Whereas HTML defines a webpage's structure and content and CSS sets the formatting and appearance, JavaScript adds interactivity to a webpage and creates rich web applications.
810 JavaScript typed arrays Guide, JavaScript
JavaScript typed arrays are array-like objects and provide a mechanism for accessing raw binary data. As you may already know, Array objects grow and shrink dynamically and can have any JavaScript value. JavaScript engines perform optimizations so that these arrays are fast. However, as web applications become more and more powerful, adding features such as audio and video manipulation, access to raw data using WebSockets, and so forth, it has become clear that there are times when it would be helpful for JavaScript code to be able to quickly and easily manipulate raw binary data in typed arrays.
811 Memory Management JavaScript, Performance, memory
Low-level languages, like C, have low-level memory management primitives like malloc() and free(). On the other hand, JavaScript values are allocated when things (objects, strings, etc.) are created and "automatically" freed when they are not used anymore. The latter process is called garbage collection. This "automatically" is a source of confusion and gives JavaScript (and other high-level languages) developers the impression they can decide not to care about memory management. This is a mistake.
812 Microsoft JavaScript extensions JavaScript, JavaScript:Microsoft Extensions, Non-standard, Reference
Microsoft browsers (Internet Explorer, and in a few cases, Microsoft Edge) support a number of special Microsoft extensions to the otherwise standard JavaScript APIs.
813 @cc_on JavaScript, JavaScript:Microsoft Extensions, Non-standard, Obsolete, Statement
The @cc_on statement activates conditional compilation support within comments in a script.
814 @if JavaScript, JavaScript:Microsoft Extensions, Non-standard, Obsolete, Reference, Statement
The @if statement conditionally executes a group of statements, depending on the value of an expression.
815 @set JavaScript, JavaScript:Microsoft Extensions, Non-standard, Obsolete, Reference, Statement
The @set statement creates variables used with conditional compilation statements.
816 ActiveXObject ActiveXObject, Deprecated, Extension, JavaScript, JavaScript:Microsoft Extensions, Microsoft, Non-standard, Obsolete, Reference
The ActiveXObject Object enables and returns a reference to an automation object.
817 Date.getVarDate JavaScript, Method, Reference
The getVarDate method returns a VT_DATE value from a Date object.
818 Debug
The debug object is an instrinsic global object that sends output to a debugger.
819 Debug.debuggerEnabled
The debug.debuggerEnabled property determines whether debugging is enabled for the script context. Debugging may be enabled or disabled whether or not a debugger is attached.
820 Debug.msTraceAsyncCallbackCompleted
Indicates that the callback stack associated with a previously specified asynchronous operation has completed.
821 Debug.msTraceAsyncCallbackCompleted
The debug.msTraceAsyncCallbackCompleted function indicates that an asynchronous operation has completed.
822 Debug.msTraceAsyncCallbackStarting
The debug.msTraceAsyncCallbackStarting function associates the callback stack with a previously specified asynchronous operation.
823 Debug.msTraceAsyncOperationStarting
Initiates a trace for an asynchronous operation.
824 Debug.msUpdateAsyncCallbackRelation
The debug.msUpdateAsyncCallbackRelation function updates the relationship status between a synchronous work item and the associated asynchronous operation.
825 Debug.setNonUserCodeExceptions
If this property is set to true in a given scope, the debugger can then determine to take some action (for example, break) on exceptions thrown inside that scope if the developer wishes to break on user-unhandled exceptions. If this property is set to false is the same as if the property was never set.
826 Debug.write
The debug.write function sends strings to the script debugger.
827 Debug.writeln Beginner, JavaScript, Method
The debug.writeln function sends strings to the script debugger, followed by a newline character.
828 Enumerator
The Enumerator object enables enumeration of items in a collection.
829 Enumerator.atEnd
The Enumerator.atEnd method returns a Boolean value indicating if the enumerator is at the end of the collection.
830 Enumerator.item
The Enumerator.item method returns the current item in the collection.
831 Enumerator.moveFirst
The Enumerator.moveFirst method resets the current item in the collection to the first item.
832 Enumerator.moveNext
The Enumerator.moveNext method moves the current item to the next item in the collection.
833 Error.description
The Error.description property returns or sets the descriptive string associated with a specific error.
834 Error.number
The Error.number property returns or sets the numeric value associated with a specific error. The Error object's default property is number.
835 Error.stackTraceLimit
The Error.stackTraceLimit property gets or sets the stack trace limit, which is equivalent to the number of error frames to display. The default limit is 10.
836 GetObject
The GetObject function returns a reference to an Automation object from a file.
837 ScriptEngine JavaScript, Method, Non-standard
The ScriptEngine function gets the name of the scripting language in use.
838 ScriptEngineBuildVersion
The ScriptEngineBuildVersion function bets the build version number of the scripting engine in use.
839 ScriptEngineMajorVersion
The ScriptEngineMajorVersion function gets the major version number of the scripting engine in use.
840 ScriptEngineMinorVersion
The ScriptEngineMinorVersion function gets the minor version number of the scripting engine in use.
841 VBArray
The VBArray object provides access to Visual Basic safe arrays.
842 VBArray.dimensions
The VBArray.dimensions method returns the number of dimensions in a VBArray.
843 VBArray.getItem
The VBArray.getItem method returns the item at the specified location.
844 VBArray.lbound
The VBArray.lbound method returns the lowest index value used in the specified dimension of a VBArray.
845 VBArray.toArray
The VBArray.toArray method returns a standard JavaScript array converted from a VBArray.
846 VBArray.ubound
The VBArray.ubound method returns the highest index value used in the specified dimension of the VBArray.
847 New in JavaScript ECMAScript, JavaScript, Versions
This chapter contains information about JavaScript's version history and implementation status for Mozilla/SpiderMonkey-based JavaScript applications, such as Firefox.
848 ECMAScript 2015 support in Mozilla ECMAScript 2015, Firefox, JavaScript
ECMAScript 2015 is the sixth edition of the ECMAScript Language Specification standard. It defines the standard for the JavaScript implementation in SpiderMonkey, the engine used in Firefox and other Mozilla applications.
849 ECMAScript 5 support in Mozilla ECMAScript 5, JavaScript, Versions
ECMAScript 5.1, an older version of the standard upon which JavaScript is based, was approved in June 2011.
850 ECMAScript Next support in Mozilla Firefox, JavaScript
ECMAScript Next refers to new features of the ECMA-262 standard (commonly referred to as JavaScript) introduced after ECMAScript 2015. New versions of ECMAScript specifications are released yearly. This year, the ES2016 specification will be released and the ES2017 is the current ECMAScript draft specification.
851 Firefox JavaScript changelog JavaScript, Versions
The following is a changelog for JavaScript features in Firefox releases.
852 New in JavaScript 1.1 JavaScript, Versions
The following is a changelog for JavaScript from Netscape Navigator 2.0 to 3.0. The old Netscape documentation references this as "Features added after version 1". Netscape Navigator 3.0 was released on August 19, 1996. Netscape Navigator 3.0 was the second major version of the browser with JavaScript support.
853 New in JavaScript 1.2 JavaScript, Versions
The following is a changelog for JavaScript from Netscape Navigator 3.0 to 4.0. The old Netscape documentation can be found on archive.org. Netscape Navigator 4.0 was released on June 11, 1997. Netscape Navigator 4.0 was the third major version of the browser with JavaScript support.
854 New in JavaScript 1.3 JavaScript, Versions
The following is a changelog for JavaScript from Netscape Navigator 4.0 to 4.5. The old Netscape documentation can be found on archive.org. Netscape Navigator 4.5 was released on October 19, 1998.
855 New in JavaScript 1.4 JavaScript, Versions
The following is a changelog for JavaScript 1.4, which was only used for Netscape's server side JavaScript released in 1999. The old Netscape documentation can be found on archive.org.
856 New in JavaScript 1.5 JavaScript, Versions
The following is a changelog for JavaScript 1.5. This version was included in Netscape Navigator 6.0 was released on November 14, 2000 and was also used in later versions of Netscape Navigator and Firefox 1.0. You can compare JavaScript 1.5 to JScript version 5.5 and Internet Explorer 5.5, which was released in July 2000. The corresponding ECMA standard is ECMA-262 Edition 3 (from December 1999).
857 New in JavaScript 1.6 JavaScript, Versions
The following is a changelog for JavaScript 1.6. This version was included in Firefox 1.5 (Gecko 1.8), which was released in November 2005. The corresponding ECMA standard is ECMA-262 Edition 3 and ECMAScript for XML (E4X) with some additional features. Several new features were introduced: E4X, several new Array methods, and Array and String generics.
858 New in JavaScript 1.7 JavaScript, Versions
The following is a changelog for JavaScript 1.7. This version was included in Firefox 2 (October 2006).
859 New in JavaScript 1.8 JavaScript, Versions
The following is a changelog for JavaScript 1.8. This version was included in Firefox 3 and is part of Gecko 1.9. See bug 380236 for a tracking development bug for JavaScript 1.8.
860 New in JavaScript 1.8.1 Firefox 3.5, JavaScript, Versions
The following is a changelog for JavaScript 1.8.1. This version was included in Firefox 3.5.
861 New in JavaScript 1.8.5 ECMAScript 5, Firefox 4, JavaScript, JavaScript 1.8.5, Versions
The following is a changelog for JavaScript 1.8.5. This version was included in Firefox 4.
862 The performance hazards of [[Prototype]] mutation JavaScript, Performance

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