freeCodeCamp/guide/english/javascript/es6/map-function/index.md

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Map Function

The Map Function

The map() function is used for creating a new array from an existing one, applying a function to each one of the elements of the first array.

The original syntax of the map function is:

  let new_arr = arr.map(function callback(currentValue, index, array) {
                  // Do some stuff with currentValue (index and array are optionals)
                })

• new_arr - the new array that is returned
• arr - the array to run the map function on
• currentValue - the current value being processed
• index - the current index of the value being processed
• array - the original array

Example (ES6):

const myArray_1 = [1, 2, 3, 4];
const myArray_2 = myArray_1.map(el => el * 2);

myArray_2 will contain the elements: [2, 4, 6, 8]

map() is a method of the Array object, so to pass that function to an iterable object it is necessary to make the object an Array.

Resources:

MDN