function*

This is an experimental technology, part of the Harmony (ECMAScript 6) proposal.
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future version of browsers as the spec changes.

Summary

Generators functions enable writing iterators more easily.

Expression
Implemented in:	Firefox 26 (SpiderMonkey 26)
ECMA Version:	ECMAScript 6th Edition (Draft)

Syntax

function* gen(i){
  while(true){
    yield i++;  
  }
}

Description

Generators are functions which can be exited and later re-entered. Their context (variable bindings) will be saved across re-entrances.

Examples

Simple example

function* idMaker(){
    var index = 0;
    while(true)
        yield index++;
}

var gen = idMaker();

console.log(gen.next().value); // 0
console.log(gen.next().value); // 1
console.log(gen.next().value); // 2
// ...

Specification

Harmony proposal
Draft spec

Feature	Chrome	Firefox (Gecko)	Internet Explorer	Opera	Safari (WebKit)
Basic support	29	26.0 (26.0)	Not supported	Not supported	Not supported

Feature	Android	Firefox Mobile (Gecko)	IE Phone	Opera Mobile	Safari Mobile
Basic support	yes (when?)	27.0 (27.0)	Not supported	Not supported	Not supported