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.
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 objectlet mp = new Map()// Adding key value pairs to the map mpmp.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 objectlet mp = new Map()// Adding key value pairs to the map mpmp.set("q", 1);mp.set("w", 2);// Value of key "q" is updated to 22mp.set("q", 22);mp.set("d", 22);mp.set("c", 12);let it = mp.keys();// Logginfg iterator objectconsole.log(it);console.log(it.next().value)// Iterator pointing to next key and // printing the valueconsole.log(it.next().value) |
Output:
MapIterator {'q', 'w', 'd', 'c'}
q
w
We have a complete list of Javascript Map Methods, to check those please go through Javascript Map Complete Reference article.
Supported Browsers:
- Chrome 38 and above
- Opera 25 and above
- Edge 12 and above
- Firefox 20 and above
- Safari 8 and above
