return
The return
statement ends function execution and specifies a value to be returned to the function caller.
Syntax
return [[expression]];
expression
- The expression to return. If omitted,
undefined
is returned instead.
Description
When a return
statement is called in a function, the execution of this function is stopped. If specified, a given value is returned to the function caller. If the expression is omitted, undefined
is returned instead. The following return statements all break the function execution:
return; return true; return false; return x; return x + y / 3;
Automatic Semicolon Insertion
The return
statement is affected by automatic semicolon insertion (ASI). No line terminator is allowed between the return
keyword and the expression.
return
a + b;
is transformed by ASI into:
return;
a + b;
The console will warn "unreachable code after return statement".
Examples
return
The following function returns the square of its argument, x
, where x
is a number.
function square(x) { return x * x; }
Interrupt a function
A function immediately stops at the point where return
is called.
function counter() { for (var count = 1; ; count++) { // infinite loop console.log(count + "A"); // until 5 if (count === 5) { return; } console.log(count + "B"); // until 4 } console.log(count + "C"); // never appears } counter(); // Output: // 1A // 1B // 2A // 2B // 3A // 3B // 4A // 4B // 5A
Returning a function
See also the article about Closures.
function magic(x) { return function calc(x) { return x * 42 }; } var answer = magic(); answer(1337); // 56154
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 1st Edition (ECMA-262) | Standard | Initial definition. |
ECMAScript 5.1 (ECMA-262) The definition of 'Return statement' in that specification. |
Standard | |
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Return statement' in that specification. |
Standard | |
ECMAScript 2017 Draft (ECMA-262) The definition of 'Return statement' in that specification. |
Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
See also
License
© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/javascript/reference/statements/return