weakMap.get

The get() method returns a specified element from a WeakMap object.

Syntax

wm.get(key);

Parameters

key

Required. The key of the element to return from the WeakMap object.

Return value

The element associated with the specified key in the WeakMap object. If the key can't be found, undefined is returned.

Examples

Using the get method

var wm = new WeakMap();
wm.set(window, 'foo');

wm.get(window); // Returns "foo".
wm.get('baz');  // Returns undefined.

Specifications

Specification	Status	Comment
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'WeakMap.prototype.get' in that specification.	Standard	Initial definition.
ECMAScript 2017 Draft (ECMA-262) The definition of 'WeakMap.prototype.get' in that specification.	Draft

Browser compatibility

Firefox-specific notes

• Prior to SpiderMonkey 38 (Firefox 38 / Thunderbird 38 / SeaMonkey 2.35), this method threw a TypeError when the key parameter was not an object. However, the ES2015 specification specifies to return undefined instead. Furthermore, WeakMap.prototype.get accepted an optional second argument as a fallback value, which is not part of the standard. Both non-standard behaviors are removed in version 38 and higher (bug 1127827).

See also

• WeakMap
• WeakMap.set()
• WeakMap.has()