What is JavaScript Map and How to Use It?

What is Map?

A Map in JavaScript stores key-value pairs, allowing keys to be of any data type. Unlike objects, it maintains the insertion order and provides built-in methods to add, get, delete, and iterate over elements efficiently.

Syntax

new Map();
new Map([iterable_objects]);

Return type: It returns a new map object.

Parameters: An array or iterable object.

Example: Creating and Using a Map

In this example, we create a Map named company with key-value pairs. The print function logs each value followed by its corresponding key using company.forEach(print).

const company = new Map([
<<<<<<< HEAD
    ["name", "Coding75"],
=======
    ["name", "Rahul"],
>>>>>>> 6c9caef (content Overview Complete)
    ["no_of_employee", 200],
    ["category", "education"]
]);
function print(key, values) {
    console.log(values + "=>" + key);
}
company.forEach(print);

Output

<<<<<<< HEAD
name=>Coding75
=======
name=>Rahul
>>>>>>> 6c9caef (content Overview Complete)
no_of_employee=>200
category=>education

Example: Iterating Over a Map Using forEach()

In this example, we create a Map named company and populate it with key-value pairs. The print function logs each value followed by its corresponding key using company.forEach(print).

const company = new Map();
<<<<<<< HEAD
company.set("name", "Coding75");
=======
company.set("name", "Rahul");
>>>>>>> 6c9caef (content Overview Complete)
company.set("no_of_employee", 200);
company.set("category", "education");
function print(key, values) {
    console.log(values + "=>" + key);
}
company.forEach(print);

Output

<<<<<<< HEAD
name=>Coding75
=======
name=>Rahul
>>>>>>> 6c9caef (content Overview Complete)
no_of_employee=>200
category=>education

JavaScript Map Properties

A JavaScript property is a member of an object that associates a key with a value.

Instance Properties

Property	Description
`constructor`	It is used to return the constructor function of Map.
`size`	Returns the number of keys and value pairs stored in a map.

JavaScript Map Methods

JavaScript methods are actions that can be performed on objects.

Instance Methods

Method	Description
`clear()`	Removes all the elements from a map and makes it empty.
`delete()`	Deletes the specified element among all the elements present in the map.
`entries()`	Returns an iterator object containing all `[key, value]` pairs of each element in the map.
`forEach()`	Executes a given function over each key-value pair in the map.
`get()`	Returns a specific element among all the elements present in a map.
`has()`	Checks whether an element with a specified key exists in a map or not.
`keys()`	Returns an iterator object of keys from a given map object.
`set()`	Adds key-value pairs to a Map object.
`values()`	Returns a new iterator object that contains the value of each element present in the Map.

Map in JS Javascript Map Reference