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WeakSet.prototype.add()

The add() method of WeakSet instances appends a new object to the end of this WeakSet.

Try it

Syntax

js
add(value)

Parameters

value

Must be either an object or a non-registered symbol. The value to add to the WeakSet collection.

Return value

The WeakSet object.

Exceptions

TypeError

Thrown if value is not an object or a non-registered symbol.

Examples

Using add

js
const ws = new WeakSet();

ws.add(window); // add the window object to the WeakSet

ws.has(window); // true

// WeakSet only takes objects as arguments
ws.add(1);
// results in "TypeError: Invalid value used in weak set" in Chrome
// and "TypeError: 1 is not a non-null object" in Firefox

Specifications

Specification
ECMAScript Language Specification
# sec-weakset.prototype.add

Browser compatibility

Desktop Mobile Server
Chrome Edge Firefox Opera Safari Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet WebView Android Deno Node.js
add 36 12 34 23 9 36 34 24 9 3.0 37 1.0 0.12.0

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet/add