Map is a collection of keyed data items, just like an Object. But the main difference is that Map allows keys of any type.

Methods and properties are:

new Map() – creates the map.
map.set(key, value) – stores the value by the key.
map.get(key) – returns the value by the key, undefined if key doesn’t exist in map. map.has(key) – returns true if the key exists, false otherwise.
map.delete(key) – removes the element (the key/value pair) by the key.
map.clear() – removes everything from the map.
map.size – returns the current element count.

For example

let map = new Map();

map.set('1', 'str1');   // a string key
map.set(1, 'num1');     // a numeric key
map.set(true, 'bool1'); // a boolean key

// remember the regular Object? it would convert keys to string
// Map keeps the type, so these two are different:
alert( map.get(1)   ); // 'num1'
alert( map.get('1') ); // 'str1'

alert( map.size ); // 3

The differences from a regular Object:

  • Any keys, objects can be keys.

  • Additional convenient methods, the size property.


Maps are a versatile and powerful data structure that provides key-value pairs for efficient data management. Maps are often a preferred choice over plain objects for tasks involving key-value associations, as they provide better control and performance.

results matching ""

    No results matching ""