WeakSet.prototype.add()

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

Try it

Syntax

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

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