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.
Example
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
WeakMapobject. value-
Any value representing the value of the entry to add to the
WeakMapobject.
Return value
The WeakMap object.
Exceptions
TypeError-
Thrown if
keyis 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
| desktop | mobile | server | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
set | ||||||||||||||