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weakMap.set

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

Syntax

wm.set(key, value);

Parameters

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

Return value

The WeakMap object.

Examples

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');

Specifications

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.	Draft

Browser compatibility

Feature	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari
Basic support	36	Yes	6¹	11²	23	8

Feature	Android webview	Chrome for Android	Edge mobile	Firefox for Android	Opera Android	iOS Safari	Samsung Internet
Basic support	36	36	Yes	6¹	23	8	?

1. Prior to Firefox 38, this method threw a TypeError when the key parameter was not an object. This has been fixed in version 38 and later to return false as per the ES2015 standard.

2. Returns 'undefined' instead of the 'Map' object.

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).