Nodejs Utililty Methods Factorial Number Get

Number.prototype.factorial = function() { 
    var n = 1;
    for(var i = 2; i <= this; i++)
        n*=i; 
    return n;
Number.prototype.permutation = function(r) { 
    return (this.factorial() / (this-r).factorial())
function permutate(p) {
    var states = new Number(p.length)
    console.log( states.permutation(states) )
function proofRow(n, pvar, rule ) {
  var s = n + "\t" + pvar + "\t" + rule
  console.log(s)
module.exports = {
  chat: function chat() {
    var argsv = chat.arguments
    var s=""
    for(var ea in argsv) {
      if(argsv[ea] != undefined)
        s += argsv[ea] + " " 
    console.log(s)
  },
  solidify: function solidify(ary) {
  for(var i in ary) {
    if(ary[i] == undefined || ary[i] == '')
      ary.splice(i,1)
  return ary
};

Number.prototype.factorial = function() { 
  if (this <= 1) return 1;
  var n = this;
  var sum = n;
  while(n > 1) sum *= --n;
  return sum;
};