JavaScript Map keys() Method (original) (raw)

Last Updated : 12 Jul, 2024

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:

**Return Value:

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

JavaScript `

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.

JavaScript `

// 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.

JavaScript `

// 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: