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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

js
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

js
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

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

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/has