Map
The Map object is a simple key/value map. Any value (both objects and primitive values) may be used as either a key or a value.
The Map[@@species] accessor property returns the Map constructor.
The Map.prototype property represents the prototype for the Map constructor.
The size accessor property returns the number of elements in a Map object.
This chapter introduces collections of data which are ordered by a key; Map and Set objects contain elements which are iterable in the order of insertion.
The clear() method removes all elements from a Map object.
The delete() method removes the specified element from a Map object.
The forEach() method executes a provided function once per each key/value pair in the Map object, in insertion order.
The get() method returns a specified element from a Map object.
The has() method returns a boolean indicating whether an element with the specified key exists or not.
The set() method adds or updates an element with a specified key and value to a Map object.
The initial value of the @@iterator property is the same function object as the initial value of the entries property.
The Map[@@toStringTag] property has an initial value of "Map".
The entries() method returns a new Iterator object that contains the [key, value] pairs for each element in the Map object in insertion order.
The keys() method returns a new Iterator object that contains the keys for each element in the Map object in insertion order.
The values() method returns a new Iterator object that contains the values for each element in the Map object in insertion order.