Array Map
Map is a collection of key data items any type of keys are allowed in Map.
The Map object holds key-value pairs and handles the same insertion order of the keys.
A Map object traverse its elements in insertion order and the method does not change the original array.
It returns the new or empty Map with the results of calling a function for every array element.
The map() method does not execute the function for array elements without values.
A Map does not contain any keys by default. It only contains the values provided by user.
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 value by the key.
map.clear() – removes everything from the map.
map.size – returns the current element count.
Program for Map:-
let map = new Map([[1 , 2], [2 ,3 ] ,[4, 5]]);
let map2 = new Map([["firstname" ,"Aman"], ["lastname", "Singh"], ["Address", "Yamunanagar"]]);
console.log(map);
console.log(map2);
Output:-
{1 => 2, 2 => 3, 4 => 5}
{"firstname" => "Aman", "lastname" => "Singh", "Address" => "Yamunanagar"}
Program for Map with set method:-
let map = new Map();
map.set('Aman', 'Singh');
map.set('Nittu', 'Singh');
map.set('Heera', 'Babu');
map.set('Singham', 'Singh');
console.log(map.size);
Output:-
4