迅雷前端求"ful"后缀那道题这样做对吗

String.prototype.get = function(suffix){
  var arr = this.split(" ");
  var obj = {};
  var sortable = [];
  for(var i = 0; i < arr.length; i++){
    if(arr[i].substring(arr[i].length-3,arr[i].length) == suffix){
      if(!obj[arr[i]]){
        obj[arr[i]] = 1;
      }
      else{
        obj[arr[i]] ++;
      }
    }
  }
  for (var vehicle in obj){  sortable.push([vehicle, obj[vehicle]])
  }
  obj = sortable.sort(function(a, b) {
    return b[1] - a[1];
  })
  var str = [];
  for(var i = 0 ; i < obj.length; i++){  str.push(obj[i][0]+"="+obj[i][1]);
  }
  return str.join(',');
}
console.log(('asful arf asful werful').get("ful"))；