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The set() method adds a new element with a specified key and value to a WeakMap object.


wm.set(key, value);


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

Return value

The WeakMap object.


Using the set method

var wm = new WeakMap();
var obj = {};

// Add new elements to the WeakMap
wm.set(obj, 'foo').set(window, 'bar'); // chainable

// Update an element in the WeakMap
wm.set(obj, 'baz');


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

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support 36 (Yes) 6.0 (6.0) 11 23 7.1
Feature Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support No support (Yes) 6.0 (6.0) No support No support 8

Firefox-specific notes

  • Prior to Firefox 33 (Firefox 33 / Thunderbird 33 / SeaMonkey 2.30), WeakMap.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).

See also

Document Tags and Contributors

 Contributors to this page: jameshkramer, nmve, kdex, fscholz, realityking, ziyunfei
 Last updated by: jameshkramer,