# A simple guide to JavaScript Array Map Method

Map is called on an existing array to return a new array based on what is returned from the function that’s passed as an argument.

Here is an example

```javascript
const names = ['Bello', 'Abdullahi', 'Abdulqudus'];

const nameLengths = names.map( name => name.length );
```

Let’s take a look at what’s happening. The .map() method works on arrays, so we have to have declared our Array, to begin with:

```javascript
// list of array 
const names = ['Bello', 'Abdullahi', 'Abdulqudus'];
```

We call `.map()`on the`names`array and pass it a function as an argument.

```javascript
names.map( name => name.length );
```

The arrow function that’s passed to`.map()`gets called *for each item* in the`names`array! The arrow function receives the first name in the array, stores it in the`name`variable and returns its length. Then it does that again for the remaining two names.

`.map()`returns a new array with the values that are returned from the arrow function.

```javascript
const nameLengths = names.map( name => name.length );
```

So `nameLengths`will be a new array`[5, 9, 10]`. This is important to understand that the .map() method doesn't modify the original arrays, it only returns a new array.