Add an item to the set
item
(*): an item to add to the set
Add multiple items to the set
items
(*[]): an array of items to be added to the set
Remove all items from the set
[items]
(*[]): an array of items to add to the set
Remove an item from the set
item
(*): the item to remove from the set
(boolean): true if the item was successfully removed, false if not
(number): The number of items in the set