Javascript **`map()`** creates a new array, which contains the results obtained from iterating over the elements of the specified array
 and calling the provided function *once* for each element in order.

>**Note**: `map()` only works on arrays. It does not execute a function for an empty array.

# Description

* **array**: the array on which the specified function is called.
* **map**: the method called for the *array* with the required parameters.

* **function(currentValue, index, arr)**: the function with its parameters which is required to run for each element of the *array*.

  * **currentValue**: the value of the current element.
  
  * **index**: the index of the current element being processed.
  * **arr**: the array object on which `map()` is called.

* **thisValue**: value to be used as the function’s `this` value when executing it. “undefined” will be passed if this value is not provided.

>**Note:** *index*, *arr* and *thisValue* are all optional parameters.

# Implementation

Now let’s take a look at an example of an implementation of the `map()` function.

//creating an array
var my_array = [1, 3, 5, 2, 4];

//map calls a function which has "item" passed as parameter
//map will pass each element of my_array as "item" in this function
//the function will double each element passed to it and return it
result = my_array.map(function(item) {
  return item*2;
});

//prints new list containing the doubled values
console.log(result); 

>**Note:** Since a new array is returned at the end, `map()` does not change the original array.

The above example didn't use any additional parameters. 

Let's look at an example with optional parameters passed into the function:

var my_array = [1,3,5,2,4];

my_array.map(function(item,index,arr) {
  console.log("item: " + item + " at index: " + index + " in the array: " + arr);
});

How to use the map function in Javascript

Javascript map() creates a new array, which contains the results obtained from iterating over the elements of the specified array and calling the provided function once for each element in order.  Note: map() only works on arrays. It does not execute a function for an empty array.  

How to use the map function in Javascript

Syntax

Description

Implementation