JS:Glossary

From MDC

actual argument

A value that is passed to a function during a function call. When an object is passed, it is passed as an object reference. See also formal argument.

anonymous function

A function without a function name.

array

A sequence of values. An array is an Array object. Sometimes, the term "array" is used to refer to an object that has array-like qualities, namely it has numerical property names and a length property.

argument

An input to a function. Primitive arguments are passed "by value" - they are sent as copies to the function. Object arguments are passed "by reference" - an object reference to the object is sent to the function.

boolean

A primitive with two possible values: true and false. The Boolean object is a wrapper around a boolean primitive.

call

See function call.

closure

code

The source code that is written by the programmer.

constant

constructor

convert

When used in the context of primitive to object or object to primitive conversions, a typecast.

compile

A synonym for parse, when JavaScript is to be interpreted by an engine.

compile time

The time from when the program is first loaded and until the program is parsed.

datatype

deep copy

derive

Document Object Model (DOM)

An API for XML and HTML documents. The DOM is not part of JavaScript. JavaScript scripts within browsers have a binding to the DOM, whereby JavaScript can call DOM methods and otherwise interact with the DOM, and window is the global object.

engine

The JavaScript engine is an interpreter that parses and executes a JavaScript program.

error

An exception. Syntax error's are explictly specified as "syntax errors".

exception

execute

To carry out a programming instruction. Happens during runtime.

expression

formal argument

A placeholder within a function that is assigned an actual argument during a function call. A formal argument acts as a variable local to the function.

function

A body of code that can be called by other code or by itself, or a variable that refers to the function. When a function is called, arguments are passed to the function as input, and the function can optionally return an output. A function is also an object. See Functions.

function call

An execution of a function's code. A function is passed

function declaration

function expression

function name

An identifier that is declared as part of a function declaration or function expression. The scope this identifier is in depends on whether it is a declaration or expression.

global object

global scope

global variable

A variable in global scope. Such a variable is a property of the global object.

identifier

A sequence of characters in the code that identifies a variable, function, or property. Identifiers must start with a letter, "$", or "_", and can contain alphanumerical characters, "$", and "_". An identifier differs from a string in that a string is data, while an identifier is part of the code. In JavaScript, there is no way to convert identifiers to strings, but it is possible to parse strings into identifiers in certain cases.

implement

immutable

Incapable of being changed.

infinity

A number value representing infinity. See Infinity.

inner function

A function within another function, which in turn is denoted as an outer function.

instance

An object created by a constructor is an instance of that constructor.

instance property, instance method

A property or method of all instances of a constructor, defined on that constructor's prototype. See also static property, static method.

internal

An object or data that cannot be directly accessed and operated on by the program, yet is necessary for the program's execution.

interpret, interpreter

See execute.

list

See array.

local, local scope

A variable or formal argument is local to a scope.

local variable

A variable that is in local scope.

method

A function that is a property of an object. Since functions themselves are objects, a method is actually an object reference to a function.

mutable

Capable of being changed.

NaN

A number value representing Not-a-Number. See NaN.

null

number

A primitive with the value of a real number. Specifically, it has a double precision floating point value. The Number object is a wrapper around a number primitive.

object

In the context of a constructor, an instance of that constructor. Otherwise, an unordered collection of properties. To be more specific, an object is an associative array, where the keys are property names, and the values are property values. All objects are derived from Object, including arrays, and Object itself is also an object.

object-oriented programming (OOP)

A paradigm in which data is encapsulated within objects and the object itself is operated on, rather than its constituent parts. JavaScript is heavily object-oriented. It follows a prototype-based model.

object reference

A link to an object. Object references can be used as if they were the objects they link to. The concept of object references arises when assigning the same object to more than one property. Each assigned property does not hold a copy of the object. Instead, they hold object references that link to the same object. In practice, this means that if the object is modified, all properties referring to the object reflect the modification.

operand

operator

outer function

A function containing a function, which in turn is denoted as an inner function.

parameter

See argument.

parent object

The object a property is the property of.

parse, parser

To analyze and convert the program into an internal format which the JavaScript engine can work upon efficiently. In JavaScript, this is done during compile-time. and in certain cases where the parser is invoked, such as during a call to the eval method.

pass

Inputting to a function during a function call, e.g. an argument is passed to a function.

primitive, primitive value

A data that is not an object and does not have any methods. JavaScript has 5 primitive datatypes: string, number, boolean, null, undefined. With the exception of null and undefined, all primitives values have object equivalents which wrap around the primitive values, e.g. a String object wraps around a string primitive. All primitives are immutable.

program

The whole code to be interpreted and executed.

property

Part of an object. A property has a name and a value. The name is a string. The value can a primitive, method, or object reference. It is often stated that a property holds an object - this is shorthand for saying the property holds a reference to the object, as properties cannot directly hold the objects themselves. In the case of the property holding an object, there is a distinction between the property's value and the object due to the nature of object references - the property's value can be changed when it's set to another value, but this does not modify the previously referred object in any way.

prototype

recursion

An act of a function calling itself.

regular expression, regexp

reference

In the context of objects, an object reference. Otherwise, the JavaScript reference itself.

run

See execute.

runtime

Everything after compile-time.

scope

script

A synonym for program, typically used when JavaScript is embedded within a document.

statement

static property, static method

A property or method of a constructor, as opposed to an instance property or instance method.

string

A primitive with an immutable sequence of characters as its value. The String object is a wrapper around a string primitive.

syntax

syntax error

type

See datatype.

type conversion, typecast

undefined

A primitive value automatically assigned to just-declared variables and formal arguments for which there are no actual arguments.

value

In the context of data or an object wrapper around that data, the primitive value that the object wrapper contains. In the context of a variable or property, something that can be either a primitive or an object reference.

variable

A placeholder where a value can be stored. In JavaScript, variables are actually properties. Variables are typically accessed through identifiers. See also global variable and local variable.

wrapper, wrap

An object that contains a primitive and whose sole purpose is to provide methods and properties to operate on that primitive. The wrapper's toString method returns the primitive.