JavaScript Map entries() Method

JavaScript Map.entries() method is used for returning an iterator object which contains all the [key, value] pairs of each element of the map. It returns the [key, value] pairs of all the elements of a map in the order of their insertion.

The Map.entries() method does not require any argument to be passed and returns an iterator object of the map. 

Syntax:

mapObj.entries();

Parameters:

• It does not require any parameters to be passed.

Return value:

• The Map.entries() method returns the [key, value] pairs of all the elements of a map in the order of their insertion.

Example 1: In this example, a map object “myMap” has been created with three [key, value] pairs, and an iterator object “iterator_obj” method is created which uses Map. entries() method to return the [key, value] pairs of all the elements of a map in the order of their insertion. 

// creating a map object
let myMap = new Map();

// Adding [key, value] pair to the map
myMap.set(0, 'geeksforgeeks');
myMap.set(1, 'is an online portal');
myMap.set(2, 'for geeks');

// creating an iterator object using Map.entries() method
let iterator_obj = myMap.entries();

// displaying the [key, value] pairs of all the elements of the map
console.log(iterator_obj.next().value);
console.log(iterator_obj.next().value);
console.log(iterator_obj.next().value);

[ 0, 'geeksforgeeks' ]
[ 1, 'is an online portal' ]
[ 2, 'for geeks' ]

Example 2: In this example, a map object “myMap” has been created with three [key, value] pairs, and an iterator object “iterator_obj” method is created which uses Map. entries() method to return the [key, value] pairs of all the elements of a map in the order of their insertion. 

// creating a map object
let myMap = new Map();

// Adding [key, value] pair to the map
myMap.set(0, 'Maps');
myMap.set(1, 'in JavaScript');

// creating an iterator object using Map.entries() method
let iterator_obj = myMap.entries();

// displaying the [key, value] pairs of all the elements of the map
console.log(iterator_obj.next().value);
console.log(iterator_obj.next().value);

[ 0, 'Maps' ]
[ 1, 'in JavaScript' ]

Applications:

Whenever we want to get all the [key, value] pairs of each element of a map using an iterator object, we use the Map.entries() method. 

Exceptions:

• If the variable is not of the Map type then the Map.entries() operation throws a TypeError.
• If the “iterator_obj.next().value” is used more times as compared to [key, value] pairs of a map, the Map.entries() method returns undefined for all those cases.

Supported Browsers:

• Google Chrome 38
• Edge 12
• Firefox 20
• Opera 25
• Safari 8