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


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


The function name. Can be omitted, in which case the function is anonymous. The name is only local to the function body.
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.


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

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


Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'function*' in that specification.
Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
The definition of 'function*' in that specification.
Living Standard  

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) (Yes) 26.0 (26.0) ? ? 10
yield* (Yes) ? 27.0 (27.0) ? ? 10
Trailing comma in parameters ? ? 52.0 (52.0) ? ? ?
Feature Android Chrome for Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support ? (Yes) (Yes) 26.0 (26.0) ? ? 10
yield* ? (Yes) ? 27.0 (27.0) ? ? 10
Trailing comma in parameters ? ? ? 52.0 (52.0) ? ? ? ?

See also

Document Tags and Contributors

 Contributors to this page: Qqwy, jameshkramer, arai, XMO, kdex, fscholz, imconfig
 Last updated by: Qqwy,