The next() method returns an object with two properties done and value. You can also provide a parameter to the next method to send a value to the generator.

Syntax

gen.next(value)

Parameters

value
The value to send to the generator. The value will be assigned as a result of a yield expression. i.e in [variable] = yield [expression], the value passed to the .next function will be assigned to [variable]

Return value

An Object with two properties:

  • done (boolean)
    • Has the value true if the iterator is past the end of the iterated sequence. In this case value optionally specifies the return value of the iterator.
    • Has the value false if the iterator was able to produce the next value in the sequence. This is equivalent of not specifying the done property altogether.
  • value - any JavaScript value returned by the iterator. Can be omitted when done is true.

Examples

Using next()

The following example shows a simple generator and the object that the next method returns:

function* gen() { 
  yield 1;
  yield 2;
  yield 3;
}

var g = gen(); // "Generator { }"
g.next();      // "Object { value: 1, done: false }"
g.next();      // "Object { value: 2, done: false }"
g.next();      // "Object { value: 3, done: false }"
g.next();      // "Object { value: undefined, done: true }"

Sending values to the generator

In this example, next is called with a value. Note that the first call did not log anything, because the generator was not yielding anything initially.

function* gen() {
  while(true) {
    var value = yield null;
    console.log(value);
  }
}

var g = gen();
g.next(1); 
// "{ value: null, done: false }"
g.next(2); 
// 2
// "{ value: null, done: false }"

Specifications

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

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung InternetNode.js
Basic supportChrome Full support 39Edge Full support 13Firefox Full support 26IE No support NoOpera Full support YesSafari Full support 10WebView Android Full support YesChrome Android Full support YesEdge Mobile Full support 13Firefox Android Full support 26Opera Android Full support YesSafari iOS Full support 10Samsung Internet Android Full support Yesnodejs Full support Yes

Legend

Full support  
Full support
No support  
No support

See also

Document Tags and Contributors

Last updated by: gilbertKaradja,