JavaScript Map keys() Method

The Map.keys() method is used to extract the keys from a given map object and return the iterator object of keys. The keys are returned in the order they were inserted.

Syntax:

Map.keys()

Parameters:

• This method does not accept any parameters.

Return Value:

• This returns the iterator object that contains keys in the map.

Example 1: Below is the basic example of the Map.keys() method.

let mp = new Map()
mp.set("a", 11);
mp.set("b", 2);
mp.set("c", 5);
console.log(mp.keys());

Output:

MapIterator {"a", "b", "c"}

Example 2: In this example, we will create an object and print its keys in the console.

// Creating a map using Map object
let mp = new Map()
// Adding key value pairs to the map mp
mp.set("a", 1);
mp.set("b", 2);
mp.set("c", 22);
mp.set("d", 12);
console.log("Type of mp.keys() is: ", typeof (mp.keys()));
console.log("Keys in map mp are: ", mp.keys());

Output:

Type of mp.keys() is:  object
Keys in map mp are:  MapIterator {'a', 'b', 'c', 'd'}

Example 3: Updating the value of the key in the map and printing values using the iterator object.

// Creating a map using Map object
let mp = new Map()
// Adding key value pairs to the map mp
mp.set("q", 1);
mp.set("w", 2);
// Value of key "q" is updated to 22
mp.set("q", 22);
mp.set("d", 22);
mp.set("c", 12);
let it = mp.keys();
// Logginfg iterator object
console.log(it);
console.log(it.next().value)
// Iterator pointing to next key and 
// printing the value
console.log(it.next().value)

Output: 

MapIterator {'q', 'w', 'd', 'c'}
q
w

Supported Browsers:

• Chrome
• Opera
• Edge
• Firefox
• Safari