function* expression

The function* keyword can be used to define a generator function inside an expression.


function* [name]([param1[, param2[, ..., paramN]]]) {


name Optional
The function name. Can be omitted, in which case the function is anonymous. The name is only local to the function body.
paramN Optional
The name of an argument to be passed to the function. A function can have up to 255 arguments.
The statements which comprise the body of the function.


A function* expression is very similar to and has almost the same syntax as a function* statement. The main difference between a function* expression and a function* statement is the function name, which can be omitted in function* expressions to create anonymous generator functions. See also the chapter about functions for more information.


Using function*

The following example defines an unnamed generator function and assigns it to x. The function yields the square of its argument:

let x = function*(y) {
   yield y * y;


ECMAScript (ECMA-262)
The definition of 'function*' in that specification.

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
function*Chrome Full support 49Edge Full support 12Firefox Full support 26IE No support NoOpera Full support 36Safari Full support 10WebView Android Full support 49Chrome Android Full support 49Firefox Android Full support 26Opera Android Full support 36Safari iOS Full support 10Samsung Internet Android Full support 5.0nodejs Full support 4.0.0
Trailing comma in parametersChrome Full support 58Edge Full support 79Firefox Full support 52IE No support NoOpera Full support 45Safari Full support 10WebView Android Full support 58Chrome Android Full support 58Firefox Android Full support 52Opera Android Full support 43Safari iOS Full support 10Samsung Internet Android Full support 7.0nodejs Full support 8.0.0


Full support
Full support
No support
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See also