Array.prototype[@@iterator]()

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The initial value of the @@iterator property is the same function object as the initial value of the values() property.

Syntax

arr[Symbol.iterator]()

Return value

The initial value given by the values() iterator. By default, using arr[Symbol.iterator] will return the values() function.

Examples

Iteration using for...of loop

var arr = ['a', 'b', 'c', 'd', 'e'];
var eArr = arr[Symbol.iterator]();
// your browser must support for..of loop
// and let-scoped variables in for loops
// const and var could also be used
for (let letter of eArr) {
  console.log(letter);
}

Alternative iteration

var arr = ['a', 'b', 'c', 'd', 'e'];
var eArr = arr[Symbol.iterator]();
console.log(eArr.next().value); // a
console.log(eArr.next().value); // b
console.log(eArr.next().value); // c
console.log(eArr.next().value); // d
console.log(eArr.next().value); // e

Use Case for brace notation

The use case for this syntax over using the dot notation (Array.prototype.values()) is in a case where you don't know what object is going to be ahead of time. If you have a function that takes an iterator and then iterate over the value, but don't know if that Object is going to have a [Iterable].prototype.values method. This could be a built-in object like String object or a custom object. 

function logIterable(it) {
  var iterator = it[Symbol.iterator]();
  // your browser must support for..of loop
  // and let-scoped variables in for loops
  // const and var could also be used
  for (let letter of iterator) {
      console.log(letter);
  }
}

// Array
logIterable(['a', 'b', 'c']);
// a
// b
// c

// string
logIterable('abc'); 
// a
// b
// c

Specifications

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Array.prototype[@@iterator]()' in that specification.
Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
The definition of 'Array.prototype[@@iterator]()' in that specification.
Draft

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
@@iteratorChrome Full support 38Edge Full support 12Firefox Full support 36
Full support 36
No support 27 — 36
Notes Alternate Name
Notes A placeholder property named @@iterator is used.
Alternate Name Uses the non-standard name: @@iterator
No support 17 — 27
Notes Alternate Name
Notes A placeholder property named iterator is used.
Alternate Name Uses the non-standard name: iterator
IE No support NoOpera Full support 25Safari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support 36
Full support 36
No support 27 — 36
Notes Alternate Name
Notes A placeholder property named @@iterator is used.
Alternate Name Uses the non-standard name: @@iterator
No support 17 — 27
Notes Alternate Name
Notes A placeholder property named iterator is used.
Alternate Name Uses the non-standard name: iterator
Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support 0.12

Legend

Full support  
Full support
No support  
No support
See implementation notes.
See implementation notes.
Uses a non-standard name.
Uses a non-standard name.

See also