Map.prototype.keys()

The keys() method returns a new Iterator object that contains the keys for each element in the Map object in insertion order.

Syntax

myMap.keys()

Return value

A new Map iterator object.

Examples

Using keys()

var myMap = new Map();
myMap.set('0', 'foo');
myMap.set(1, 'bar');
myMap.set({}, 'baz');

var mapIter = myMap.keys();

console.log(mapIter.next().value); // "0"
console.log(mapIter.next().value); // 1
console.log(mapIter.next().value); // Object

Specifications

Specification
ECMAScript Latest Draft (ECMA-262)
The definition of 'Map.prototype.keys' in that specification.

Browser compatibility

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DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
keysChrome Full support 38Edge Full support 12Firefox Full support 20IE No support NoOpera Full support 25Safari Full support 8WebView Android Full support 38Chrome Android Full support 38Firefox Android Full support 20Opera Android Full support 25Safari iOS Full support 8Samsung Internet Android Full support 3.0nodejs Full support 0.12

Legend

Full support  
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No support  
No support

See also

Related Topics
  1. Standard built-in objects
  2. Map
  3. Properties
    1. Map.prototype.size
    2. Map.prototype[@@toStringTag]
    3. get Map[@@species]
  4. Methods
    1. Map.prototype.clear()
    2. Map.prototype.delete()
    3. Map.prototype.entries()
    4. Map.prototype.forEach()
    5. Map.prototype.get()
    6. Map.prototype.has()
    7. Map.prototype.keys()
    8. Map.prototype.set()
    9. Map.prototype.values()
    10. Map.prototype[@@iterator]()
  5. Inheritance:
  6. Function
  7. Properties
    1. Function.arguments
    2. Function.arity
    3. Function.caller
    4. Function.displayName
    5. Function.length
    6. Function.name
    7. Function.prototype
  8. Methods
    1. Function.prototype.apply()
    2. Function.prototype.bind()
    3. Function.prototype.call()
    4. Function.prototype.isGenerator()
    5. Function.prototype.toSource()
    6. Function.prototype.toString()
  9. Object
  10. Properties
    1. Object.prototype.__count__
    2. Object.prototype.__noSuchMethod__
    3. Object.prototype.__parent__
    4. Object.prototype.__proto__
    5. Object.prototype.constructor
  11. Methods
    1. Object.prototype.__defineGetter__()
    2. Object.prototype.__defineSetter__()
    3. Object.prototype.__lookupGetter__()
    4. Object.prototype.__lookupSetter__()
    5. Object.prototype.hasOwnProperty()
    6. Object.prototype.isPrototypeOf()
    7. Object.prototype.propertyIsEnumerable()
    8. Object.prototype.toLocaleString()
    9. Object.prototype.toSource()
    10. Object.prototype.toString()
    11. Object.prototype.unwatch()
    12. Object.prototype.valueOf()
    13. Object.prototype.watch()
    14. Object.setPrototypeOf()