SOURCE

var arr = [1,5,3,2,10,15];
  function maxarr(arr,len){
      var max = [];
    arr.sort(function(a,b){
       return a-b;
   });
   for(var i=0;i<len;i++){
       max.push(arr.pop());
   }
   return max.reverse();
  }

   console.log(maxarr(arr,4));