function createArr(){
   var arr = new Array();
   arr.push.apply(arr,arguments);

   arr.toJoin = function(){
       return this.join(",");
   }
   arr.toSlice = function(start,end){//start num  //end num
       return Array.prototype.slice.call(this,start,end+1)
   }

   return arr;
}

var c = new createArr("a","b","c","d");

c.toSlice(1,4)
//["b", "c", "d"]