WeakSet() constructor

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨September 2015⁩.

The WeakSet() constructor creates WeakSet objects.

Syntax

new WeakSet()
new WeakSet(iterable)

Note: WeakSet() can only be constructed with new. Attempting to call it without new throws a TypeError.

Parameters

iterable Optional: If an iterable object is passed, all of its elements will be added to the new WeakSet. null is treated as undefined.

Examples

Using the WeakSet object

const ws = new WeakSet();
const foo = {};
const bar = {};

ws.add(foo);
ws.add(bar);

ws.has(foo); // true
ws.has(bar); // true

ws.delete(foo); // removes foo from the set
ws.has(foo); // false, foo has been removed
ws.has(bar); // true, bar is retained

Note that foo !== bar. While they are similar objects, they are not the same object. And so they are both added to the set.