How to delete first element of a map JavaScript

In this article we will learn how to delete first element of a map.

It is very common to delete first element of a map in JavaScript.

Problem

Now we have a problem, which is that we want to delete the first element of a map.

Now let's define a map like this:

// Map
const map = new Map([
    ['name', 'John'],
    ['age', 30],
]);

console.log(map);
// Map(2) { 'name' => 'John', 'age' => 30 }

And we only want to delete the first element, so the output becomes like this:

Map(1) { 'age' => 30 }

How to solve this problem?

Fortunately, we have a built-in function that deletes elements from the map called delete.

Delete first element using delete method

We can use delete() method to delete first element of map.

Example

// Map
const map = new Map([
    ['name', 'John'],
    ['age', 30],
]);

// Delete element
map.delete('name');

// Print the result:
console.log(map);

Output

Map(1) { 'age' => 30 }

Well, now what if I want to delete the first element and I don't know its key! What do I do?

Delete the first element of the map dynamically

Now I will answer the previous question, if you want to delete the first element and you don't know its key.

You can use Array.from() to get all the element in an array and then you can get first element easily.

// Map
const map = new Map([
    ['name', 'John'],
    ['age', 30]
]);

// Array with elements
const array = Array.from(map);

// First element
const firstEle = array[0];

// Print
console.log(firstEle);

Output

['name', 'john']

Now that we get the first element, we can delete it using delete.

// Map
const map = new Map([
    ['name', 'John'],
    ['age', 30]
]);

// Array with elements
const array = Array.from(map);

// First element
const firstEle = array[0];

// Delete first element by his key `[0]`
map.delete(firstEle[0]);

// Print
console.log(map);

Output

Map(1) { 'age' => 30 }

Thank you for reading

Thank you for reading my blog. 🚀