Nodejs Utililty Methods Number Calculate

"use strict";
Number.prototype.doubleDigitalize = function() {
  const numberString = this.toString();
  return numberString.length < 2 ? "0" + numberString : numberString;
};

Number.prototype.equals = function (another) {
    return this - another === 0;
};

Number.prototype.exp = function() {
  return Math.exp(this);
};

Number.prototype.fe = function(x)
  var s = x.toString();
  var point = s.search(/\./);
  if (point == -1)
    return (Math.abs(this - x) < 0.5);    
  else
...

Number.prototype.fillZero = function (len)
  var s = this.toString(10);
  while (s.length<len) s = "0" + s;
  return s;

Number.prototype.firstDigit = Number.prototype.firstDigit || function () {
  let number = this;
  while (number >= 10) {
    number = Math.floor(number / 10);
  return number;
};

Number.prototype.fix = function (n) {
    var val = String(this);
    n = Math.abs(n);
    val = val.split('.');
    val[1] = val[1] || '';
    var m = val[1].length;
    if (m < n) {
        m = n - m;
        while (m > 0) {
...

Number.prototype.fizz = function() {
    return this % 3 === 0 ? "fizz" : "";
};
Number.prototype.buzz = function() {
    return this % 5 === 0 ? "buzz" : "";
};
for (var i = 1; i <= 15; i++) {
    var candidate = Number(i).fizz() + Number(i).buzz();
    console.log(candidate ? candidate : i);
...

var num = 5;
Number.prototype.float = function(){ 
      return this.toFixed(2);
Number.prototype.int = function(){ 
      return parseInt(this) ;
console.log(num.float());
console.log(num);
...

Number.prototype.floatMethod = function() {
    return parseFloat(this).toFixed(2);
};
function convert_float() {
    var n = 60.00;
   console.log(n.floatMethod());
convert_float(n);