Simplest way for leading zero padding in JavaScript

number-pad-zero.js

Number.prototype.pad = function(size) {
  var s = String(this);
  while (s.length < (size || 2)) {s = "0" + s;}
  return s;
}

(1).pad(3) // => "001"
(10).pad(3) // => "010"
(100).pad(3) // => "100"

zeroPad(number) {
    return number > 9 ? number : '0' + number;
 }

Wow, Thank you. How can I export this function & Import it to use it in other files?