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WeakMap.prototype.get() - JavaScript | MDN
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WeakMap.prototype.get()
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The get() method of WeakMap instances returns the value corresponding to the key in this WeakMap, or undefined if there is none. Object values are returned as the same reference that was originally stored, not as a copy, so mutations to the returned object will be reflected anywhere that reference is held, including inside the WeakMap.
Try it
const weakmap = new WeakMap();
const object1 = {};
const object2 = {};
weakmap.set(object1, 42);
console.log(weakmap.get(object1));
// Expected output: 42
console.log(weakmap.get(object2));
// Expected output: undefined
Syntax
js
get(key)
Parameters
Return value
The value associated with the specified key in the WeakMap object. If the key can't be found, undefined is returned. Always returns undefined if key is not an object or a non-registered symbol.
Examples
Using get()
js
const wm = new WeakMap();
wm.set(window, "foo");
wm.get(window); // Returns "foo".
wm.get("baz"); // Returns undefined.
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-weakmap.prototype.get |
Browser compatibility
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