WeakMap.prototype.set()
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 set()
method of WeakMap
instances adds a new element with a specified key
and value to this WeakMap
.
Try it
const weakmap1 = new WeakMap();
const object1 = {};
const object2 = {};
weakmap1.set(object1, "foo");
weakmap1.set(object2, "bar");
console.log(weakmap1.get(object1));
// Expected output: "foo"
console.log(weakmap1.get(object2));
// Expected output: "bar"
Syntax
js
set(key, value)
Parameters
key
-
Must be either an object or a non-registered symbol. The key of the entry to add to the
WeakMap
object. value
-
Any value representing the value of the entry to add to the
WeakMap
object.
Return value
The WeakMap
object.
Exceptions
TypeError
-
Thrown if
key
is not an object or a non-registered symbol.
Examples
Using the set() method
js
const wm = new WeakMap();
const 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");
// Using a non-registered symbol as key
const sym = Symbol("foo");
wm.set(sym, "baz");
wm.set(Symbol.iterator, "qux");
Specifications
Specification |
---|
ECMAScript® 2025 Language Specification # sec-weakmap.prototype.set |
Browser compatibility
Report problems with this compatibility data on GitHubdesktop | mobile | server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
set |
Legend
Tip: you can click/tap on a cell for more information.
- Full support
- Full support
- See implementation notes.
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.