WeakSet.prototype.has()

The has() method of {{jsxref("WeakSet")}} instances returns a boolean indicating whether the specified value exists in this WeakSet or not.

{{InteractiveExample("JavaScript Demo: WeakSet.prototype.has()")}}

```js interactive-example const weakset = new WeakSet(); const object1 = {}; const object2 = {};

weakset.add(object1);

console.log(weakset.has(object1)); // Expected output: true

console.log(weakset.has(object2)); // Expected output: false

## Syntax

```js-nolint
has(value)

Parameters#

• value
• : The value to test for presence in the WeakSet object. Objects are compared by reference, not by value.

Return value#

Returns true if 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 has()#

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#

{{Specifications}}

Browser compatibility#

{{Compat}}

See also#

• {{jsxref("WeakSet")}}
• {{jsxref("WeakSet.prototype.add()")}}
• {{jsxref("WeakSet.prototype.delete()")}}