How to use the map() method to operate arrays in JavaScript

The JavaScript array map() method creates a new array using the result of calling the provided function on each element in this array.
Syntax

array.map(callback[, thisObject]);

The following are the details of the parameters:

callback: The function generates new array elements from the current element.

thisObject: The object used as the execution callback

Return value:

Return to create the array
Compatibility:

This method is a JavaScript extends to the ECMA-262 standard; therefore it may not exist in other implementations of the standard. To make it work, you need to add the following script code at the top:

if (!Array.prototype.map)
{
 Array.prototype.map = 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] = fun.call(thisp, this[i], i, this);
  }
 
  return res;
 };
}

Example:

This will produce the following results:

roots is : 1,2,3

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