WeakSet
A WeakSet object is a collection of unique objects (no primitive values). References to objects in a WeakSet are held weakly, so they do not prevent garbage collection if there are no other references to the object. WeakSet elements are not iterable.
add(value) function
Add a new object to the WeakSet if it is not already present. The value must be an object.
value: The object to add.
Returns: The WeakSet object (for chaining).
has(value) function
Return a boolean indicating whether an object is present in the WeakSet.
value: The object to check.
Returns: True if the object is in the WeakSet, otherwise false.
delete(value) function
Remove the specified object from the WeakSet, if it exists.
value: The object to remove.
Returns: True if the object was present and removed, otherwise false.