# Update an element in a Map using JavaScript

By Atta Ur Rehman Shah (https://attacomsian.com/about). Published Dec 4, 2022, updated Jun 7, 2023. Topics: JavaScript.
Canonical URL: https://attacomsian.com/blog/javascript-map-update-element

> Learn how to use the set() method to update an element in a Map using JavaScript.

The `set()` method is used to update or add an element's value in a `Map` object. It takes two parameters: the key and the new value. If the `Map` object already contains the key, the `set()` method updates its value. Otherwise, it adds a new key-value pair to the `Map`.

```javascript
const map = new Map([
  ['name', 'Alex'],
  ['scores', [75, 87]],
  ['bio', { age: 27, country: 'Pakistan' }]
])

console.log(map)
// Map(3) {
//   'name' => 'Alex',
//   'scores' => [75, 87],
//   'bio' => { age: 27, country: 'Pakistan' }
// }

// Update name (STRING)
map.set('name', 'Alex Hales')
console.log(map.get('name')) // Alex Hales

// Update scores (ARRAY)
map.set('scores', [...map.get('scores'), 99])
console.log(map.get('scores')) // [75, 87, 99]

// Update bio (OBJECT)
map.set('bio', { ...map.get('bio'), job: 'Engineer' })

console.log(map.get('bio'))
// { age: 27, country: 'Pakistan', job: 'Engineer' }
```

In the above example, the `name`, `scores`, and `bio` elements are updated with new values using the `set()` method. The `name` is updated with a string value, `scores` with an array value by spreading the existing scores and adding a new score of 99, and `bio` with an object value by spreading the existing bio object and adding a `job` property.

You can also use the `set()` method to add new elements to a `Map` object:

```javascript
const map = new Map([
  ['name', 'Alex'],
  ['scores', [75, 87]],
  ['bio', { age: 27, country: 'Pakistan' }]
])

map.set('email', 'alex@example.com')

console.log(map)
// Map(4) {
//   'name' => 'Alex',
//   'scores' => [75, 87],
//   'bio' => { age: 27, country: 'Pakistan' },
//   'email' => 'alex@example.com'
// }
```

In this case, the `email` element is added to the `Map` object with its corresponding value.

To learn more about the `Map` object and how to utilize it to create collections of key-value pairs in JavaScript, you can refer to [this article](https://attacomsian.com/blog/maps-javascript).