A Map is a sequential collection of key-value pairs, almost identical to an
array used in a similar context. Keys can be any type, but must be unique.
Values are replaced if added to the map using the same key.
Strengths
Keys and values can be any type, including objects.
Supports array syntax (square brackets).
Insertion order is preserved.
Performance and memory efficiency is very similar to an array.
Automatically frees allocated memory when its size drops low enough.
Weaknesses
Can’t be converted to an array when objects are used as keys.