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Language core Widely available

Generators

Generator functions (function*) create iterators that return multiple values, one after another, on-demand.

Language core

Overview

Generator functions (function*) create iterators that return multiple values, one after another, on-demand.

Browser support

Feature Desktop Mobile
Chrome
Edge
Firefox
Safari
Chrome Android
Safari iOS
Generator
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Generator.next

The next() method of Generator instances 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.
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Generator.return

The return() method of Generator instances acts as if a return statement is inserted in the generator's body at the current suspended position, which finishes the generator and allows the generator to perform any cleanup tasks when combined with a try...finally block.
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Generator.throw

The throw() method of Generator instances acts as if a throw statement is inserted in the generator's body at the current suspended position, which informs the generator of an error condition and allows it to handle the error, or perform cleanup and close itself.
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Other
javascript.builtins.GeneratorFunction

The GeneratorFunction object provides methods for generator functions. In JavaScript, every generator function is actually a GeneratorFunction object.
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Built-in object
GeneratorFunction.GeneratorFunction

The GeneratorFunction() constructor creates GeneratorFunction objects.
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Other
javascript.operators.generator_function

`function*` expression
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Operator
trailing comma

Trailing comma in parameters
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Other
javascript.operators.yield

The yield operator is used to pause and resume a generator function.
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javascript.operators.yield_star

`yield*`
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javascript.statements.generator_function

`function*` statement
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Statement
IteratorResult object

`IteratorResult` object instead of throwing
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not constructable with new

Not constructable with `new` (ES2016)
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trailing comma in parameters

Trailing comma in parameters
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1+Supported (version) Not supported ※Has note Sub-feature descriptions sourced from MDN Web Docs (CC BY-SA 2.5)
Notes 2 item(s)
Implementation note
  • Starting with Firefox 33, the parsing of the `yield` expression has been updated to conform with the ES2015 specification.
  • Starting with Firefox 29, an `IteratorResult` object returned for completed generator function.
Notes 1 item(s)
Implementation note
  • Starting with Firefox 33, the parsing of the `yield` expression has been updated to conform with the ES2015 specification.

Syntax

JAVASCRIPT 
function* fibonacci() {
  let [a, b] = [0, 1];
  while (true) {
    yield a;
    [a, b] = [b, a + b];
  }
}

const fib = fibonacci();
fib.next().value; // 0
fib.next().value; // 1
fib.next().value; // 1
fib.next().value; // 2

Live demo

steprungenerator

Processing one timeStop, one timebetween per and to next. Value generatesimul-tion.. with yield

PreviewFullscreen

nonenumbershi-kens

none to continueshi-kens from, main taiming in value 1 getout..

PreviewFullscreen

de-ta. Sequentialprocessing

big de-tasett array, generator Usesplit to processing..

PreviewFullscreen

Use cases

  • Using Generators

    Generator functions (function*) create iterators that return multiple values, one after another, on-demand.

Cautions

  • No specific concerns. Stable across all major browsers.

Accessibility

  • When updating the DOM dynamically, announce important changes to assistive technology with aria-live regions.

Related links

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