Javascript String removeSubstring(a, n)

String.prototype.removeSubstring = function (a, n) {
 var arr = [];//from   www  . j  a v a 2 s  .  c om
 arr = str.split('');
 arr.sort();

 //console.log(arr);
 console.log("oldStr = '" + str + "'");

 var count = 0;

 for (var i = 0; i < arr.length; i++) {
  if( n != null ) {
   if(arr[i] === a)
    arr.splice(i, n)
    i = arr.length;
  } else {
   while(arr[i] === a) {
    arr.splice(i, 1)
   }
  }
 }
 //console.log(arr);
 var tostring = arr.join('');
 console.log("newStr = '" + tostring + "'");
}

var str = 'aaa';

var newStr1 = str.removeSubstring('a', 2); // newStr = 'a'

var str = 'aaabbbba';

var newStr2 = str.removeSubstring('a'); // newStr = 'bbbb'