The has() method of WeakSet instances returns a boolean indicating whether an object exists in this WeakSet or not.
WeakSet.prototype.has()
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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https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet/has