Array Reordering - map

                      This method is really very useful and often time we will use in our project.

It calls the function for each element of the array and returns the array of results. It does not change the original array.

Syntax:

let result = arr.map(function(item, index, array) {
  // returns the new value instead of item

})

item      -   The value of the current element and its mandatory.
index    -   The array index of the current element and its an optional parameter.

array    -   The array object the current element belongs to the array and its an optional.

let lengths = ["One", "Two", "Three"];
var lengthTest = lengths.map(item => item.length)
alert(lengthTest); // 3,3,5