WeakMap.prototype.has()

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

Return value: Returns true if an entry 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.

Parameters: key The key of the entry to test for presence in the WeakMap object. Object keys are compared by reference, not by value.

Syntax example: has(key)