《剑指offer》— JavaScript（3）从尾到头打印链表

/*function ListNode(x){
    this.val = x;
    this.next = null;
}*/
function printListFromTailToHead(head)
{
    var res=[];
    while(head){
        res.unshift(head.val);
        head=head.next;
    }
    return res;
}

function  LinkedList(){
   var Node=function(val){
         this.val=val;
         this.next=null;
   }

   var length=0;
   var head=null;

   this.append=function(val){
      var node=new Node(val),
          current;
      if (head==null) {
          head=node;
      }else{
          current=head;

          while(current.next){
              current=current.next;
          }

          current.next=node;
      }

      length++;
   };

   this.removeAt=function(pos){
         if (pos>-1 && pos<length) {
        var current=head,
            previous,
            index=0;

        if (pos===0) {
           head=current.next;
        }else{
            while(index++<pos){
                previous=current;
                current=current.next;
            }
            length--;
            previous.next=current.next;
        }
         }else{
             return null;
         }
   };

   this.insertAt=function(pos,val){
           if (pos>=0 && pos <=length) {
               var node=new Node(),
                   current=head,
                   previous,
                   index=0;

            if (pos===0) {
                head=node;
            }else{
                while(index++<pos){
                    previous=current;
                    current=current.next;
                }
                node.next=current;
                previous.next=node;
            }
            length++;
            return true;
           }else{
               return null;
           }
   };

}