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The set() method adds or updates an element with a specified key and value to a Map object.


myMap.set(key, value);


Required. The key of the element to add to the Map object.
Required. The value of the element to add to the Map object.

Return value

The Map object.


Using the set method

var myMap = new Map();

// Add new elements to the map
myMap.set('bar', 'foo');
myMap.set(1, 'foobar');

// Update an element in the map
myMap.set('bar', 'baz');


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

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support 38 (Yes) 13.0 (13.0) 11 25 7.1
Feature Android Chrome for Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support No support 38 (Yes) 13.0 (13.0) No support No support 8

Compatibility notes

  • Prior to Firefox 33 (Firefox 33 / Thunderbird 33 / SeaMonkey 2.30), Map.prototype.set returned undefined and was not chainable. This has been fixed (bug 1031632). The behavior can be found in Chrome/v8 as well (issue). This behavior can also be found in IE11.

See also

Document Tags and Contributors

 Last updated by: jameshkramer,