双向链表的实现

    function Node(element) {
        this.element = element;
        this.next = null;
        this.previous = null;
    }
    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;
    }
    function find(item) {
        var currNode = this.head;
        while (currNode.element != item) {
            currNode = currNode.next;
        }
        return currNode;
    }
    function insert(newElement, item) {//在item后面插入新节点
        var newNode = new Node(newElement);
        var current = this.find(item);
        newNode.next = current.next;
        newNode.previous = current;
        current.next = newNode;
    }
    function display() {
        var currNode = this.head;
        while (!(currNode.next == null)) {
            document.write(currNode.next.element + " ");
            currNode = currNode.next;
        }
    }
    function remove(item) {
        var currNode = this.find(item);
        if ((currNode.element != null) && (currNode.next == null)) {
            currNode.previous.next = null;
            currNode.previous = null;
        } else if (currNode.element != null) {
            currNode.previous.next = currNode.next;//当前节点的前一个节点的链接指向当前节点的后一个节点            
            currNode.next.previous = currNode.previous;//当前节点的后一个节点的链接指向当前节点的前一个节点
            currNode.next = null;//将当前节点的后向指针置空
            currNode.previous = null;//将当前节点的前向指针置空 
        }
    }
    
    function findLast() {
        var currNode = this.head;
        while (currNode.next != null) {//针对于只有一个空节点的情况
            currNode = currNode.next;
        }
        return currNode;
    }
    //反序显示双向链表中的元素
    function dispReverse() {
        var currNode = this.head;
        currNode = this.findLast();
        while (currNode.previous != null) {//head节点的前向指针指向null
            document.write(currNode.element + " ");
            currNode = currNode.previous;
        }
    }
    var cities = new LList();
    cities.insert("Conway", "head");
    cities.insert("Russellville", "Conway");
    cities.insert("Carlisle", "Russellville");
    cities.insert("Alma", "Carlisle");
    cities.display();
    document.write("<br />");
    cities.remove("Alma");
    cities.display();
    document.write("<br />");
    cities.dispReverse();
    document.write("<br />");
    cities.remove("Conway");
    cities.display();