/** * 实现在链表中向前移动n个节点和向后移动n个节点 *  * *///链表节点function Node(element){    this.element = element;    this.next = null;    this.previous = null;}//链表function LList(){    this.head = new Node(‘head‘);    this.find = find;    this.insert = insert;    this.display = display;    this.remove = remove;    this.findLast = findLast;    this.dispReverse = dispReverse;    //当前节点就是头节点    this.currentNode = this.head;    //从链表开头向前移动n个节点    this.advance = advance;    //从链表某个节点向后回退n个节点    this.back = back;    //显示当前节点    this.show = show;}//倒序输出链表中的所有节点function dispReverse(){    var currNode = this.head;    currNode = this.findLast();    while (!(currNode.previous == null)){        document.write(currNode.element + ‘&nbsp;‘);        currNode = currNode.previous;    }}//找到最后一个节点function findLast(){    var currNode = this.head;    while (!(currNode.next == null)){        currNode = currNode.next;    }    return currNode;}//删除某一个节点function remove(item){    var currNode = this.find(item);    if(!(currNode.next == null)){        currNode.previous.next = currNode.next;        currNode.next.previous = currNode.previous;        currNode.next = null;        currNode.previous = null;    }}//打印所有链表节点function display(){    var currNode = this.head;    while (!(currNode.next == null)){        document.write(currNode.next.element + ‘&nbsp;‘);        currNode = currNode.next;    }}//找到某一个节点function find(item){    var currNode = this.head;    while (currNode.element != item){        currNode = currNode.next;    }    return currNode;}//插入某一个节点function insert(newElement , item){    var newNode = new Node(newElement);    var current = this.find(item);    newNode.next = current.next;    newNode.previous = current;    current.next = newNode;}//在链表中向前移动n个节点function advance(n){    while ((n>0) && !(this.currentNode.next==null)){        this.currentNode = this.currentNode.next;         n--    }}//在链表中向后移动n个节点function back(n){    while (n>0 && !(this.currentNode.element==‘head‘)){        this.currentNode = this.currentNode.previous;        n--;    }}//显示当前节点function show(){    document.write(this.currentNode.element);}var cities = new LList();cities.insert(‘Conway‘,‘head‘);cities.insert(‘Russellville‘, ‘Conway‘);cities.insert(‘Carlisle‘, ‘Russellville‘);cities.insert(‘Alma‘ , ‘Carlisle‘);cities.insert(‘dezhou‘ , ‘Alma‘);cities.insert(‘alasijia‘ , ‘dezhou‘);cities.display();document.write(‘<br>‘);cities.show();cities.advance(4);document.write(‘<br>‘);cities.show();cities.back(2);document.write(‘<br>‘);cities.show();