The has() method of WeakMap instances returns a boolean indicating whether an element with the specified key exists in this WeakMap or not.

Syntax

has(key)

Parameters

• key
  • : The key of the element to test for presence in the WeakMap object.

Return value

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

Examples

Using the has method

const wm = new WeakMap();
wm.set(window, "foo");

wm.has(window); // returns true
wm.has("baz"); // returns false

Specifications

Browser compatibility

See also

• WeakMap
• WeakMap.prototype.set
• WeakMap.prototype.get