How to use array map in JavaScript

In this article, I am going to explain array map() in JavaScript.
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Array map method in JavaScript

The JavaScript array map method creates a new array with the result of provided function on every element in this array.

Syntax of array map method[, thisArgs);

Parameters in array map method:

  • arrary

    Array required an array object.

  • callback

    Callback function accepts up to three arguments, and callback function is produce an element of the new array from the array of current one.

  • thisArgs

    ThisArgs is used as this when executing callbacks.

Return value in map method

A new array in which each element is the callback function return value for the associated original element.

Exception in map  method

If callback argument is not a function object, A TypeError exception is fire.

There are the following callback function parameter:

Parameter Value
value Array element value.
index Numeric  index of the array element.

Example of array map method:

<!DOCTYPE html>



<title>JavaScript Array map()</title>



<script type="text/javascript">

    if (! { = function (fun /*, thisp*/) {

            var len = this.length;

            if (typeof fun != "function")

                throw new TypeError();


            var res = new Array(len);

            var thisp = arguments[1];

            for (var i = 0; i < len; i++) {

                if (i in this)

                    res[i] =, this[i], i, this);


            return res;

        };   }

    var numbers = [1, 2, 5];

    var roots =;


    document.write("roots is : " + roots);






roots is : 1,1.4142135623730951,2.23606797749979

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