Javascript Array uniqu2() method

var arr=[1,2,2,5,5,5,5,5,3,3,3,4,4,4,4];

Array.prototype.uniqu2=function(){
 this.sort();/*from   w  w w  . j  a v a 2s .com*/
 var newArr=[];
 for(var i=0;i<this.length;i++){
  var start=this.indexOf(this[i]);
  var end=this.lastIndexOf(this[i]);
  if(start==end){
   newArr.push(this[i]);
  }
  else{
   newArr.push(this[i],this[i]);
  }
  i=end;
 }
 return newArr;
}


arr.uniqu2();