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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
orcontinue
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
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Update compatibility data on GitHub
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Legacy generator function | Chrome No support No | Edge No support No | Firefox No support 2 — 58 | IE No support No | Opera No support No | Safari No support No | WebView Android No support No | Chrome Android No support No | Edge Mobile No support No | Firefox Android No support 4 — 58 | Opera Android No support No | Safari iOS No support No | Samsung Internet Android No support No | nodejs No support No |
async function | Chrome Full support 55 | Edge Full support Yes | Firefox Full support 52 | IE No support No | Opera Full support 42 | Safari Full support 10.1 | WebView Android Full support Yes | Chrome Android Full support 55 | Edge Mobile Full support Yes | Firefox Android Full support 52 | Opera Android Full support 42 | Safari iOS Full support 10.1 | Samsung Internet Android Full support 6.0 | nodejs
Full support
7.6.0
|
block | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
break | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
class | Chrome Full support 42 | Edge Full support Yes | Firefox Full support 45 | IE No support No | Opera Full support 36 | Safari Full support 10.1 | WebView Android Full support 42 | Chrome Android Full support 42 | Edge Mobile Full support Yes | Firefox Android Full support 45 | Opera Android ? | Safari iOS Full support 10.1 | Samsung Internet Android Full support 4.0 | nodejs Full support 6.0.0 |
const | Chrome Full support 21 | Edge Full support Yes | Firefox
Full support
36
| IE Full support 11 | Opera Full support Yes | Safari Full support 5.1 | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android
Full support
36
| Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
continue | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
debugger | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
do...while | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support 6 | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
Empty statement (; ) | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
export | Chrome Full support 61 | Edge
Full support
16
| Firefox
Full support
60
| IE No support No | Opera Full support 47 | Safari Full support 10.1 | WebView Android No support No | Chrome Android Full support 61 | Edge Mobile Full support Yes | Firefox Android
Full support
60
| Opera Android Full support 47 | Safari iOS Full support 10.1 | Samsung Internet Android No support No | nodejs ? |
for | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
for await...of | Chrome Full support 63 | Edge No support No | Firefox Full support 57 | IE No support No | Opera Full support 50 | Safari Full support 11 | WebView Android Full support 63 | Chrome Android Full support 63 | Edge Mobile No support No | Firefox Android ? | Opera Android Full support 50 | Safari iOS ? | Samsung Internet Android ? | nodejs ? |
for each...in | Chrome No support No | Edge No support No | Firefox No support 1.5 — 57 | IE No support No | Opera No support No | Safari No support No | WebView Android No support No | Chrome Android No support No | Edge Mobile No support No | Firefox Android No support 4 — 57 | Opera Android No support No | Safari iOS No support No | Samsung Internet Android No support No | nodejs No support No |
for...in | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support 6 | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
for...of | Chrome Full support 38 | Edge Full support 12 | Firefox
Full support
13
| IE No support No | Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support Yes | Edge Mobile Full support 12 | Firefox Android
Full support
14
| Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support Yes | nodejs Full support Yes |
function | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
function* | Chrome Full support 39 | Edge Full support 13 | Firefox Full support 26 | IE No support No | Opera Full support 26 | Safari Full support 10 | WebView Android Full support Yes | Chrome Android Full support 39 | Edge Mobile Full support Yes | Firefox Android Full support 26 | Opera Android Full support Yes | Safari iOS Full support 10 | Samsung Internet Android Full support 4.0 | nodejs
Full support
4.0.0
|
if...else | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
import | Chrome Full support 61 | Edge
Full support
16
| Firefox
Full support
60
| IE No support No | Opera Full support 47 | Safari Full support 10.1 | WebView Android Full support 61 | Chrome Android Full support 61 | Edge Mobile Full support Yes | Firefox Android
Full support
60
| Opera Android Full support 47 | Safari iOS Full support 10.1 | Samsung Internet Android No support No | nodejs
Full support
8.5.0
|
import.meta | Chrome Full support 64 | Edge ? | Firefox Full support 62 | IE No support No | Opera Full support 51 | Safari ? | WebView Android Full support 64 | Chrome Android Full support 64 | Edge Mobile ? | Firefox Android Full support 62 | Opera Android Full support 51 | Safari iOS ? | Samsung Internet Android No support No | nodejs ? |
label | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
let | Chrome
Full support
49
| Edge Full support 12 | Firefox
Full support
44
| IE Full support 11 | Opera Full support 17 | Safari Full support 10 | WebView Android
Full support
49
| Chrome Android
Full support
49
| Edge Mobile Full support 12 | Firefox Android
Full support
44
| Opera Android Full support 17 | Safari iOS Full support 10 | Samsung Internet Android Full support 4.0 | nodejs Full support 6.0.0 |
return | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
switch | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
throw | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
try...catch | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support 6 | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
var | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
while | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
with | Chrome Full support Yes | Edge Full support Yes | Firefox Full support 1 | IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Edge Mobile Full support Yes | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs 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.