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A Map holds key-value pairs where the keys can be any datatype.

A Map remembers the original insertion order of the keys.

A Map has a property that represents the size of the map.

Map Methods

MethodDescription new Map()Creates a new Map object set()Sets the value for a key in a Map get()Gets the value for a key in a Map clear()Removes all the elements from a Map delete()Removes a Map element specified by a key has()Returns true if a key exists in a Map forEach()Invokes a callback for each key/value pair in a Map entries()Returns an iterator object with the [key, value] pairs in a Map keys()Returns an iterator object with the keys in a Map values()Returns an iterator object of the values in a Map PropertyDescription sizeReturns the number of Map elements

How to Create a Map

You can create a JavaScript Map by:

Passing an Array to new Map()

Create a Map and use Map.set()

new Map()

You can create a Map by passing an Array to the new Map() constructor:

Example

// Create a Map
const fruits = new Map([
["apples", 500],
["bananas", 300],
["oranges", 200]
Try it Yourself »

Map.set()

You can add elements to a Map with the set() method:

Example

// Create a Map
const fruits = new Map();
// Set Map Values
fruits.set("apples", 500);
fruits.set("bananas", 300);
fruits.set("oranges", 200);
Try it Yourself »

The set() method can also be used to change existing Map values:

Example

fruits.set("apples", 500); Try it Yourself »

Map.get()

The get() method gets the value of a key in a Map:

Example

fruits.get("apples");    // Returns 500
Try it Yourself »

Map.entries()

The entries() method returns an iterator object with the [key,values] in a Map:

Example

// List all entries
let text = "";
for (const x of fruits.entries()) {
text += x;
Try it Yourself »

Map.keys()

The keys() method returns an iterator object with the keys in a Map:

Example

// List all keys
let text = "";
for (const x of fruits.keys()) {
text += x;
Try it Yourself »

Map.values()

The values() method returns an iterator object with the values in a Map:

Example

// List all values
let text = "";
for (const x of fruits.values()) {
text += x;
Try it Yourself »

You can use the values() method to sum the values in a Map:

Example

// Sum all values
let total = 0;
for (const x of fruits.values()) {
total += x;
Try it Yourself » const apples = {name: 'Apples'};
const bananas = {name: 'Bananas'};
const oranges = {name: 'Oranges'};
// Create a Map
const fruits = new Map();
// Add new Elements to the Map
fruits.set(apples, 500);
fruits.set(bananas, 300);
fruits.set(oranges, 200);
Try it Yourself »

Remember: The key is an object (apples), not a string ("apples"):

Example

fruits.get("apples");  // Returns undefined
Try it Yourself »

Browser Support

JavaScript Maps are supported in all browsers, except Internet Explorer:

Report Error

If you want to report an error, or if you want to make a suggestion, do not hesitate to send us an e-mail:

[email protected]

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