How are elements ordered in a Map in JavaScript ?

In JavaScript, a new object called Map was introduced in the ES6 version. A map is a collection of elements where each element is stored in a key, value pair. Map objects can store both objects as well as primitive data types. The elements of a map are iterable. Elements are always iterated in the insertion order.

The elements in a map are ordered which means that the elements can be iterated in the order they are inserted.

Syntax:

new Map([it])

Example 1:  In this example, we will create a new map object and iterate over it to check how the elements are ordered.

Javascript

var sample = new Map();
sample.set("name", "Rahul");
sample.set("age", 20);
sample.set("Country", "India");
for(var [key, value] of sample){
    console.log(`Key = ${key}, Value=${value}`)
}

Output:

Key = name, Value=Rahul
Key = age, Value=20
Key = Country, Value=India

Example 2:  In this example, we will save the keys and values of the map in two different arrays 

Javascript

var sample = new Map();
sample.set("name", "Rahul");
sample.set("age", 20);
sample.set("Country", "India");
var keys = sample.keys();
var val = sample.values()
var arr= [];
var arr2 = [];
for (var ele of keys){
    arr.push(ele)
}
console.log(arr);
for (var ele of val){
    arr2.push(ele)
}
console.log(arr2);

Output:

(3) ['name', 'age', 'Country']
(3) ['Rahul', 20, 'India']

Explanation: We can see that the elements maintain the order they are entered in the map so the insertion in new arrays follows the same order as that of the map