About this Reference

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.

The JavaScript language is intended to be used within some larger environment, be it a browser, server-side scripts, or similar. For the most part, this reference attempts to be environment-agnostic and does not target a web browser environment.

Where to find JavaScript information

JavaScript documentation of core language features (pure ECMAScript, for the most part) includes the following:

If you are new to JavaScript, start with the guide. Once you have a firm grasp of the fundamentals, you can use the reference to get more details on individual objects and language constructs.

Structure of the reference

In the JavaScript reference you can find the following chapters:

Standard built-in objects
This chapter documents all the JavaScript standard built-in objects, along with their methods and properties.
Statements and declarations
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.
Expressions and operators
This chapter documents all the JavaScript language operators, expressions and keywords.
Functions
Chapter about JavaScript functions.
Classes
Chapter about JavaScript classes introduced in ECMAScript 2015.
Errors
Chapter about specific errors, exceptions and warnings thrown by JavaScript.
New in JavaScript
Chapter about JavaScript version history.

More reference pages

Global Objects

Functions and function scope

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.

Statements and declarations by category

For an alphabetical listing see the sidebar on the left.

Control flow

Block
A block statement is used to group zero or more statements. The block is delimited by a pair of curly brackets.
break
Terminates the current loop, switch, or label statement and transfers program control to the statement following the terminated statement.
continue
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.
Empty
An empty statement is used to provide no statement, although the JavaScript syntax would expect one.
if...else
Executes a statement if a specified condition is true. If the condition is false, another statement can be executed.
switch
Evaluates an expression, matching the expression's value to a case clause, and executes statements associated with that case.
throw
Throws a user-defined exception.
try...catch
Marks a block of statements to try, and specifies a response, should an exception be thrown.

Declarations

var
Declares a variable, optionally initializing it to a value.
let
Declares a block scope local variable, optionally initializing it to a value.
const
Declares a read-only named constant.

Functions and classes

function
Declares a function with the specified parameters.
function*
Generator Functions enable writing iterators more easily.
async function
Declares an async function with the specified parameters.
return
Specifies the value to be returned by a function.
class
Declares a class.

Iterations

do...while
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.
for
Creates a loop that consists of three optional expressions, enclosed in parentheses and separated by semicolons, followed by a statement executed in the loop.
for each...in
Iterates a specified variable over all values of object's properties. For each distinct property, a specified statement is executed.
for...in
Iterates over the enumerable properties of an object, in arbitrary order. For each distinct property, statements can be executed.
for...of
Iterates over iterable objects (including arrays, array-like objects, iterators and generators), invoking a custom iteration hook with statements to be executed for the value of each distinct property.
for await...of
Iterates over async iterable objects, array-like objects, iterators and generators, invoking a custom iteration hook with statements to be executed for the value of each distinct property.
while
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.

Others

debugger
Invokes any available debugging functionality. If no debugging functionality is available, this statement has no effect.
export
Used to export functions to make them available for imports in external modules, and other scripts.
import
Used to import functions exported from an external module, another script.
import.meta
A meta-property exposing context-specific metadata to a JavaScript module.
label
Provides a statement with an identifier that you can refer to using a break or continue statement.
with
Extends the scope chain for a statement.

Specifications

Specification Status Comment
ECMAScript 1st Edition (ECMA-262)
The definition of 'Statements' in that specification.
Standard Initial definition
ECMAScript 3rd Edition (ECMA-262)
The definition of 'Statements' in that specification.
Standard  
ECMAScript 5.1 (ECMA-262)
The definition of 'Statements' in that specification.
Standard  
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'ECMAScript Language: Statements and Declarations' in that specification.
Standard New: function*, let, for...of, yield, class
ECMAScript Latest Draft (ECMA-262)
The definition of 'ECMAScript Language: Statements and Declarations' in that specification.
Draft  

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
Legacy generator function
DeprecatedNon-standard
Chrome No support NoEdge No support NoFirefox No support 2 — 58IE No support NoOpera No support NoSafari No support NoWebView Android No support NoChrome Android No support NoEdge Mobile No support NoFirefox Android No support 4 — 58Opera Android No support NoSafari iOS No support NoSamsung Internet Android No support Nonodejs No support No
async functionChrome Full support 55Edge Full support YesFirefox Full support 52IE No support NoOpera Full support 42Safari Full support 10.1WebView Android Full support YesChrome Android Full support 55Edge Mobile Full support YesFirefox Android Full support 52Opera Android Full support 42Safari iOS Full support 10.1Samsung Internet Android Full support 6.0nodejs Full support 7.6.0
Full support 7.6.0
Full support 7.0.0
Disabled
Disabled From version 7.0.0: this feature is behind the --harmony runtime flag.
blockChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
breakChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
classChrome Full support 42Edge Full support YesFirefox Full support 45IE No support NoOpera Full support 36Safari Full support 10.1WebView Android Full support 42Chrome Android Full support 42Edge Mobile Full support YesFirefox Android Full support 45Opera Android ? Safari iOS Full support 10.1Samsung Internet Android Full support 4.0nodejs Full support 6.0.0
constChrome Full support 21Edge Full support YesFirefox Full support 36
Notes
Full support 36
Notes
Notes Prior to Firefox 13, const is implemented, but re-assignment is not failing.
Notes Prior to Firefox 46, a TypeError was thrown on redeclaration instead of a SyntaxError.
IE Full support 11Opera Full support YesSafari Full support 5.1WebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 36
Notes
Full support 36
Notes
Notes Prior to Firefox 13, const is implemented, but re-assignment is not failing.
Notes Prior to Firefox 46, a TypeError was thrown on redeclaration instead of a SyntaxError.
Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
continueChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
debuggerChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
do...whileChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support 6Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
Empty statement (;)Chrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
exportChrome Full support 61Edge Full support 16
Full support 16
Full support 15
Disabled
Disabled From version 15: this feature is behind the Experimental JavaScript Features preference.
Firefox Full support 60
Full support 60
No support 54 — 60
Disabled
Disabled From version 54 until version 60 (exclusive): this feature is behind the dom.moduleScripts.enabled preference. To change preferences in Firefox, visit about:config.
IE No support NoOpera Full support 47Safari Full support 10.1WebView Android No support NoChrome Android Full support 61Edge Mobile Full support YesFirefox Android Full support 60
Full support 60
No support 54 — 60
Disabled
Disabled From version 54 until version 60 (exclusive): this feature is behind the dom.moduleScripts.enabled preference. To change preferences in Firefox, visit about:config.
Opera Android Full support 47Safari iOS Full support 10.1Samsung Internet Android No support Nonodejs ?
forChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
for await...of
Experimental
Chrome Full support 63Edge No support NoFirefox Full support 57IE No support NoOpera Full support 50Safari Full support 11WebView Android Full support 63Chrome Android Full support 63Edge Mobile No support NoFirefox Android ? Opera Android Full support 50Safari iOS ? Samsung Internet Android ? nodejs ?
for each...in
DeprecatedNon-standard
Chrome No support NoEdge No support NoFirefox No support 1.5 — 57IE No support NoOpera No support NoSafari No support NoWebView Android No support NoChrome Android No support NoEdge Mobile No support NoFirefox Android No support 4 — 57Opera Android No support NoSafari iOS No support NoSamsung Internet Android No support Nonodejs No support No
for...inChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support 6Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
for...ofChrome Full support 38Edge Full support 12Firefox Full support 13
Notes
Full support 13
Notes
Notes Prior to Firefox 51, using the for...of loop construct with the const keyword threw a SyntaxError ("missing = in const declaration").
IE No support NoOpera Full support 25Safari Full support 8WebView Android Full support 38Chrome Android Full support YesEdge Mobile Full support 12Firefox Android Full support 14
Notes
Full support 14
Notes
Notes Prior to Firefox 51, using the for...of loop construct with the const keyword threw a SyntaxError ("missing = in const declaration").
Opera Android Full support 25Safari iOS Full support 8Samsung Internet Android Full support Yesnodejs Full support Yes
functionChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
function*Chrome Full support 39Edge Full support 13Firefox Full support 26IE No support NoOpera Full support 26Safari Full support 10WebView Android Full support YesChrome Android Full support 39Edge Mobile Full support YesFirefox Android Full support 26Opera Android Full support YesSafari iOS Full support 10Samsung Internet Android Full support 4.0nodejs Full support 4.0.0
Full support 4.0.0
Full support 0.12
Disabled
Disabled From version 0.12: this feature is behind the --harmony runtime flag.
if...elseChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
importChrome Full support 61Edge Full support 16
Full support 16
Full support 15
Disabled
Disabled From version 15: this feature is behind the Experimental JavaScript Features preference.
Firefox Full support 60
Full support 60
No support 54 — 60
Disabled
Disabled From version 54 until version 60 (exclusive): this feature is behind the dom.moduleScripts.enabled preference. To change preferences in Firefox, visit about:config.
IE No support NoOpera Full support 47Safari Full support 10.1WebView Android Full support 61Chrome Android Full support 61Edge Mobile Full support YesFirefox Android Full support 60
Full support 60
No support 54 — 60
Disabled
Disabled From version 54 until version 60 (exclusive): this feature is behind the dom.moduleScripts.enabled preference. To change preferences in Firefox, visit about:config.
Opera Android Full support 47Safari iOS Full support 10.1Samsung Internet Android No support Nonodejs Full support 8.5.0
Notes Disabled
Full support 8.5.0
Notes Disabled
Notes files must have suffix .mjs, not .js
Disabled From version 8.5.0: this feature is behind the --experimental-modules runtime flag.
import.metaChrome Full support 64Edge ? Firefox Full support 62IE No support NoOpera Full support 51Safari ? WebView Android Full support 64Chrome Android Full support 64Edge Mobile ? Firefox Android Full support 62Opera Android Full support 51Safari iOS ? Samsung Internet Android No support Nonodejs ?
labelChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
letChrome Full support 49
Full support 49
No support 48 — 49
Notes Disabled
Notes Support outside of strict mode.
Disabled From version 48 until version 49 (exclusive): this feature is behind the Enable Experimental JavaScript Features preference. To change preferences in Chrome, visit chrome://flags.
No support 41 — 49
Notes
Notes Strict mode is required.
Edge Full support 12Firefox Full support 44
Notes
Full support 44
Notes
Notes Prior to Firefox 44, let is only available to code blocks in HTML wrapped in a <script type="application/javascript;version=1.7"> block (or higher version) and has different semantics (e.g. no temporal dead zone).
Notes Prior to Firefox 46, a TypeError is thrown on redeclaration instead of a SyntaxError.
Notes Firefox 54 adds support of let in workers.
IE Full support 11Opera Full support 17Safari Full support 10WebView Android Full support 49
Full support 49
No support 41 — 49
Notes
Notes Strict mode is required.
Chrome Android Full support 49
Full support 49
No support 48 — 49
Notes Disabled
Notes Support outside of strict mode.
Disabled From version 48 until version 49 (exclusive): this feature is behind the Enable Experimental JavaScript Features preference. To change preferences in Chrome, visit chrome://flags.
No support 41 — 49
Notes
Notes Strict mode is required.
Edge Mobile Full support 12Firefox Android Full support 44
Notes
Full support 44
Notes
Notes Prior to Firefox 44, let is only available to code blocks in HTML wrapped in a <script type="application/javascript;version=1.7"> block (or higher version) and has different semantics (e.g. no temporal dead zone).
Notes Prior to Firefox 46, a TypeError is thrown on redeclaration instead of a SyntaxError.
Notes Firefox 54 adds support of let in workers.
Opera Android Full support 17Safari iOS Full support 10Samsung Internet Android Full support 4.0nodejs Full support 6.0.0
returnChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
switchChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
throwChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
try...catchChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support 6Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
varChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
whileChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
with
Deprecated
Chrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
Non-standard. Expect poor cross-browser support.
Non-standard. Expect poor cross-browser support.
Deprecated. Not for use in new websites.
Deprecated. Not for use in new websites.
See implementation notes.
See implementation notes.
User must explicitly enable this feature.
User must explicitly enable this feature.

See also

Operators and other keywords

This chapter documents all the JavaScript language operators, expressions and keywords.

Expressions and operators by category

For an alphabetical listing see the sidebar on the left.

Primary expressions

Basic keywords and general expressions in JavaScript.

this
The this keyword refers to a special property of an execution context.
function
The function keyword defines a function expression.
class
The class keyword defines a class expression.
function*
The function* keyword defines a generator function expression.
yield
Pause and resume a generator function.
yield*
Delegate to another generator function or iterable object.
async function
The async function defines an async function expression.
await
Pause and resume an async function and wait for the promise's resolution/rejection.
[]
Array initializer/literal syntax.
{}
Object initializer/literal syntax.
/ab+c/i
Regular expression literal syntax.
( )
Grouping operator.

Left-hand-side expressions

Left values are the destination of an assignment.

Property accessors
Member operators provide access to a property or method of an object
(object.property and object["property"]).
new
The new operator creates an instance of a constructor.
new.target
In constructors, new.target refers to the constructor that was invoked by new.
super
The super keyword calls the parent constructor.
...obj
Spread syntax allows an expression to be expanded in places where multiple arguments (for function calls) or multiple elements (for array literals) are expected.

Increment and decrement

Postfix/prefix increment and postfix/prefix decrement operators.

A++
Postfix increment operator.
A--
Postfix decrement operator.
++A
Prefix increment operator.
--A
Prefix decrement operator.

Unary operators

A unary operation is operation with only one operand.

delete
The delete operator deletes a property from an object.
void
The void operator discards an expression's return value.
typeof
The typeof operator determines the type of a given object.
+
The unary plus operator converts its operand to Number type.
-
The unary negation operator converts its operand to Number type and then negates it.
~
Bitwise NOT operator.
!
Logical NOT operator.

Arithmetic operators

Arithmetic operators take numerical values (either literals or variables) as their operands and return a single numerical value.

+
Addition operator.
-
Subtraction operator.
/
Division operator.
*
Multiplication operator.
%
Remainder operator.
**
Exponentiation operator.

Relational operators

A comparison operator compares its operands and returns a Boolean value based on whether the comparison is true.

in
The in operator determines whether an object has a given property.
instanceof
The instanceof operator determines whether an object is an instance of another object.
<
Less than operator.
>
Greater than operator.
<=
Less than or equal operator.
>=
Greater than or equal operator.

Note: => is not an operator, but the notation for Arrow functions.

Equality operators

The result of evaluating an equality operator is always of type Boolean based on whether the comparison is true.

==
Equality operator.
!=
Inequality operator.
===
Identity operator.
!==
Nonidentity operator.

Bitwise shift operators

Operations to shift all bits of the operand.

<<
Bitwise left shift operator.
>>
Bitwise right shift operator.
>>>
Bitwise unsigned right shift operator.

Binary bitwise operators

Bitwise operators treat their operands as a set of 32 bits (zeros and ones) and return standard JavaScript numerical values.

&
Bitwise AND.
|
Bitwise OR.
^
Bitwise XOR.

Binary logical operators

Logical operators are typically used with boolean (logical) values, and when they are, they return a boolean value.

&&
Logical AND.
||
Logical OR.

Conditional (ternary) operator

(condition ? ifTrue : ifFalse)

The conditional operator returns one of two values based on the logical value of the condition.

Assignment operators

An assignment operator assigns a value to its left operand based on the value of its right operand.

=
Assignment operator.
*=
Multiplication assignment.
/=
Division assignment.
%=
Remainder assignment.
+=
Addition assignment.
-=
Subtraction assignment
<<=
Left shift assignment.
>>=
Right shift assignment.
>>>=
Unsigned right shift assignment.
&=
Bitwise AND assignment.
^=
Bitwise XOR assignment.
|=
Bitwise OR assignment.
[a, b] = [1, 2]
{a, b} = {a:1, b:2}

Destructuring assignment allows you to assign the properties of an array or object to variables using syntax that looks similar to array or object literals.

Comma operator

,
The comma operator allows multiple expressions to be evaluated in a single statement and returns the result of the last expression.

Non-standard features

Expression closures Obsolete since Gecko 60
The expression closure syntax is a shorthand for writing simple function.
Legacy generator function Obsolete since Gecko 58
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 contains at least one yield expression.
[for (x of y) x] Obsolete since Gecko 58
Array comprehensions.
(for (x of y) y) Obsolete since Gecko 58
Generator comprehensions.

Specifications

Specification Status Comment
ECMAScript 1st Edition (ECMA-262)
The definition of 'Expressions' in that specification.
Standard Initial definition
ECMAScript 5.1 (ECMA-262)
The definition of 'Expressions' in that specification.
Standard  
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'ECMAScript Language: Expressions' in that specification.
Standard New: Spread syntax, rest syntax, destructuring assignment, super keyword.
ECMAScript Latest Draft (ECMA-262)
The definition of 'ECMAScript Language: Expressions' in that specification.
Draft  

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
Array comprehensions
DeprecatedNon-standard
Chrome No support NoEdge No support NoFirefox No support 30 — 58IE No support NoOpera No support NoSafari No support NoWebView Android No support NoChrome Android No support NoEdge Mobile No support NoFirefox Android No support 30 — 58Opera Android No support NoSafari iOS No support NoSamsung Internet Android No support Nonodejs No support No
async function expressionChrome Full support 55Edge Full support 15Firefox Full support 52IE No support NoOpera Full support 42Safari Full support 10.1WebView Android Full support 55Chrome Android Full support 55Edge Mobile Full support 15Firefox Android Full support 52Opera Android Full support 42Safari iOS Full support 10.1Samsung Internet Android Full support 6.0nodejs Full support 7.6.0
Full support 7.6.0
Full support 7.0.0
Disabled
Disabled From version 7.0.0: this feature is behind the --harmony runtime flag.
awaitChrome Full support 55Edge Full support YesFirefox Full support 52IE ? Opera Full support 42Safari Full support 10.1WebView Android Full support 55Chrome Android Full support 55Edge Mobile Full support YesFirefox Android Full support 52Opera Android Full support 42Safari iOS Full support 10.1Samsung Internet Android Full support 6.0nodejs Full support 7.6.0
Full support 7.6.0
Full support 7.0.0
Disabled
Disabled From version 7.0.0: this feature is behind the --harmony runtime flag.
classChrome Full support 42Edge Full support YesFirefox Full support 45IE No support NoOpera Full support YesSafari Full support YesWebView Android Full support 42Chrome Android Full support 42Edge Mobile Full support YesFirefox Android Full support 45Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support 4.0nodejs Full support 6.0.0
Full support 6.0.0
Full support 5.0.0
Disabled
Disabled From version 5.0.0: this feature is behind the --harmony runtime flag.
Comma operatorChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support 3Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
Conditional operator (c ? t : f)Chrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
deleteChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
Destructuring assignmentChrome Full support 49Edge Full support 14Firefox Full support 41
Notes
Full support 41
Notes
Notes Firefox provided a non-standard destructuring implementation from Firefox 2 to 40.
IE No support NoOpera Full support YesSafari Full support 8WebView Android Full support 49Chrome Android Full support 49Edge Mobile Full support 14Firefox Android Full support 41
Notes
Full support 41
Notes
Notes Firefox provided a non-standard destructuring implementation from Firefox 2 to 40.
Opera Android Full support YesSafari iOS Full support 8Samsung Internet Android Full support 5.0nodejs Full support 6.0.0
Expression closures
DeprecatedNon-standard
Chrome No support NoEdge No support NoFirefox No support 3 — 60IE No support NoOpera No support NoSafari No support NoWebView Android No support NoChrome Android No support NoEdge Mobile No support NoFirefox Android No support 4 — 60Opera Android No support NoSafari iOS No support NoSamsung Internet Android No support Nonodejs No support No
functionChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
function*Chrome Full support YesEdge Full support YesFirefox Full support 26IE No support NoOpera Full support YesSafari Full support 10WebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 26Opera Android Full support YesSafari iOS Full support 10Samsung Internet Android Full support Yesnodejs Full support Yes
Generator comprehensions
DeprecatedNon-standard
Chrome No support NoEdge No support NoFirefox No support 30 — 58IE No support NoOpera No support NoSafari No support NoWebView Android No support NoChrome Android No support NoEdge Mobile No support NoFirefox Android No support 30 — 58Opera Android No support NoSafari iOS No support NoSamsung Internet Android No support Nonodejs No support No
Grouping operator ()Chrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
inChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
instanceofChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
Legacy generator function
DeprecatedNon-standard
Chrome No support NoEdge No support NoFirefox No support 2 — 58IE No support NoOpera No support NoSafari No support NoWebView Android No support NoChrome Android No support NoEdge Mobile No support NoFirefox Android No support 4 — 58Opera Android No support NoSafari iOS No support NoSamsung Internet Android No support Nonodejs No support No
newChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
new.targetChrome Full support 46Edge Full support YesFirefox Full support 41IE No support NoOpera Full support YesSafari Full support YesWebView Android Full support 46Chrome Android Full support 46Edge Mobile Full support YesFirefox Android Full support 41Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support 5.0nodejs Full support 5.0.0
Object initializerChrome Full support 1Edge Full support YesFirefox Full support 1IE Full support 1Opera Full support YesSafari Full support 1WebView Android Full support 1Chrome Android Full support 18Edge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support 1Samsung Internet Android Full support Yesnodejs Full support Yes
Pipeline operator (|>)
Experimental
Chrome No support NoEdge No support NoFirefox Full support 58
Disabled
Full support 58
Disabled
Disabled From version 58: this feature is behind the --enable-pipeline-operator compile flag.
IE No support NoOpera No support NoSafari No support NoWebView Android No support NoChrome Android No support NoEdge Mobile No support NoFirefox Android Full support 58
Disabled
Full support 58
Disabled
Disabled From version 58: this feature is behind the --enable-pipeline-operator compile flag.
Opera Android No support NoSafari iOS No support NoSamsung Internet Android No support Nonodejs No support No
Property accessorsChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
superChrome Full support 42Edge Full support YesFirefox Full support 45IE No support NoOpera Full support YesSafari Full support YesWebView Android Full support 42Chrome Android Full support 42Edge Mobile Full support YesFirefox Android Full support 45Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support 4.0nodejs Full support Yes
thisChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
typeofChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
voidChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
yieldChrome Full support 39Edge Full support YesFirefox Full support 26
Notes
Full support 26
Notes
Notes Starting with Firefox 33, the parsing of the yield expression has been updated to conform with the ES2015 specification.
IE No support NoOpera Full support YesSafari Full support 10WebView Android Full support 39Chrome Android Full support 39Edge Mobile Full support YesFirefox Android Full support 26
Notes
Full support 26
Notes
Notes Starting with Firefox 33, the parsing of the yield expression has been updated to conform with the ES2015 specification.
Opera Android Full support YesSafari iOS Full support 10Samsung Internet Android Full support 4.0nodejs Full support 4.0.0
Full support 4.0.0
Full support 0.12
Disabled
Disabled From version 0.12: this feature is behind the --harmony runtime flag.
yield*Chrome Full support YesEdge Full support YesFirefox Full support 27
Notes
Full support 27
Notes
Notes Starting with Firefox 33, the parsing of the yield expression has been updated to conform with the ES2015 specification.
IE No support NoOpera Full support YesSafari Full support 10WebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 27
Notes
Full support 27
Notes
Notes Starting with Firefox 33, the parsing of the yield expression has been updated to conform with the ES2015 specification.
Opera Android Full support YesSafari iOS Full support 10Samsung Internet Android Full support Yesnodejs Full support 4.0.0
Full support 4.0.0
Full support 0.12
Disabled
Disabled From version 0.12: this feature is behind the --harmony runtime flag.

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
Non-standard. Expect poor cross-browser support.
Non-standard. Expect poor cross-browser support.
Deprecated. Not for use in new websites.
Deprecated. Not for use in new websites.
See implementation notes.
See implementation notes.
User must explicitly enable this feature.
User must explicitly enable this feature.

See also

Comments

E4X (extension)

Global statements:

Global functions:

Global constructors:

Appendix A - Reserved Words

Appendix B - Deprecated Features

Document Tags and Contributors

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