W3cubDocs

WeakSet.prototype.has()

The has() method of WeakSet instances returns a boolean indicating whether an object exists in this WeakSet or not.

Try it

Syntax

has(value)

Parameters

value: The value to test for presence in the WeakSet.

Return value

Returns true if an element with the specified value exists in the WeakSet object; otherwise false. Always returns false if value is not an object or a non-registered symbol.

Examples

Using the `has()` method

const ws = new WeakSet();
const obj = {};
ws.add(window);

ws.has(window); // returns true
ws.has(obj); // returns false

// Storing a non-registered symbol
const sym = Symbol("foo");
ws.add(sym);
ws.add(Symbol.iterator);

Specifications

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

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
`has`	36	12	34	23	9	36	34	24	9	3.0	37	1.0	0.12.0