Nodejs Utililty Methods String Count

var a = new String();
var b = new String("Hello World");
var c = new String("ABC");
String.prototype.count = function() { return this.length; }
result = a=="" && b=="Hello World" && c.count()==3;

String.prototype.count = function(c) {
  var count = 0;
  for(var i = 0; i < this.length; i += 1) {
    if(this[i] === c) { count += 1; }
  return count;
};

String.prototype.count=function(c) { 
  var result = 0, i = 0;
  for(i;i<this.length;i++)if(this[i]==c)result++;
  return result;
};
function commonCharacterCount(s1, s2) {
    var chars = [];
    var total = 0;
    for(var i = 0; i < s1.length; i++){
...

String.prototype.count=function(s1) {   
    return (this.length - this.replace(new RegExp(s1,"g"), '').length) / s1.length;  

String.prototype.count=function(s1) { 
    return (this.length - this.replace(new RegExp(s1,"g"), '').length) / s1.length;
String.prototype.trunc = String.prototype.trunc ||
function(n){
  return this.length>n ? this.substr(0,n-1)+'...' : this;
};
Array.prototype.remove = function(from, to) {
  var rest = this.slice((to || from) + 1 || this.length);
...

String.prototype.count = function(string) {
  return this.split(string).length - 1;
};

String.prototype.countAll = function (letter) {
  var letterCount = 0
  for (var i = 0; i < this.length; i++) {
    if (this.charAt(i).toUpperCase() == letter.toUpperCase()){
      letterCount++
  return letterCount
var sen = 'Come on, get up and fight'
console.log(sen.countAll('o'))