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# Array.prototype.map()

The **`map()`** method **creates
a new array** populated with the results of calling a provided function on
every element in the calling array.

## Syntax

```js
// Arrow function
map((element) => { /* … */ })
map((element, index) => { /* … */ })
map((element, index, array) => { /* … */ })

// Callback function
map(callbackFn)
map(callbackFn, thisArg)

// Inline callback function
map(function (element) { /* … */ })
map(function (element, index) { /* … */ })
map(function (element, index, array) { /* … */ })
map(function (element, index, array) { /* … */ }, thisArg)
```

### Parameters

- `callbackFn`

  - : A function to execute for each element in the array. Its return value is added as a single element in the new array.

    The function is called with the following arguments:

    - `element`
      - : The current element being processed in the array.
    - `index`
      - : The index of the current element being processed in the array.
    - `array`
      - : The array `map()` was called upon.

- `thisArg` _**optional**_
  - : A value to use as `this` when executing `callbackFn`. 

### Return value

A new array with each element being the result of the callback function.

## Description

The `map()` method is an iterative method. It calls a provided `callbackFn` function once for each element in an array and constructs a new array from the results.

`callbackFn` is invoked only for array indexes which have assigned values. It is not invoked for empty slots in sparse arrays.

The `map()` method is a copying method. It does not alter `this`. However, the function provided as `callbackFn` can mutate the array. Note, however, that the length of the array is saved _before_ the first invocation of `callbackFn`. Therefore:

- `callbackFn` will not visit any elements added beyond the array's initial length when the call to `map()` began.
- Changes to already-visited indexes do not cause `callbackFn` to be invoked on them again.
- If an existing, yet-unvisited element of the array is changed by `callbackFn`, its value passed to the `callbackFn` will be the value at the time that element gets visited. [Deleted](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Operators/delete) elements are not visited.



The `map()` method is generic. It only expects the `this` value to have a `length` property and integer-keyed properties.

Since `map` builds a new array, calling it without using the returned
array is an anti-pattern; use [`Array.prototype.forEach()`](./forEach.mdx) or
`for...of` instead.
