双向链表

双向链表结构:

先在Html引入js文件:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>TEST</title>
    <script src="./04_双向链表.js"></script>
</head>
<body>
</body>
</html>

双向链表.js

let LinkedList = function(){
    let head = null
    let length = 0
    //定义一个辅助节点类
    let Node = function(element){
        this.previous = null
        this.element = element
        this.next = null
    }
    //在链表后面追加
    this.append = function(element){
        let node = new Node(element)
        let current = head
        if(length == 0){
            head = node
        }else{
            while(current.next){
                current = current.next
            }
            node.previous = current
            current.next = node

        }
        length++
        return head;
    }
    //链表在某个地方插入
    this.insertNode = function(element,position){
        let node = new Node(element)
        let current = head
        if(position>=0&&position<length){
            if(position==0){
                head = node
                current.previous = head
                head.next = current
            }else{
                let last = null
                let index = 0
                while(index<position){
                    last = current
                    current = current.next
                    index++;
                }
                //设置好新节点的previous和next
                node.previous = last
                node.next = current
                //分别设置之前前节点的下一个目标为node,后节点的上一个目标为node
                current.previous = node
                last.next = node
            }
            length++;
            return current;
        }
        return null;
    }

    //链表在某个位置删除元素
    this.removeatNode = function(position){
        let current = head
        if(position>=0&&position<length){
            if(position==0){
                head = current.next;
                if(head){
                head.previous = null;
                }
            }else{
                let index = 0
                let last = null
                while(index<position){
                    last = current
                    current = current.next
                    index++;
                }
                last.next = current.next
                if(current.next){
                current.next.previous = last
                }
            }
            length--;
            return current;
        }
        return null;
    }

    //链表获取元素位置
    this.indexOf = function(element){
        let index = 0
        let current = head
        while(current){
            if(current.element==element){
                return index;
            }
            current = current.next
            index++
        }
        return -1;
    }

    //链表删除元素
    this.removeNode = function(element){
        return this.removeatNode(this.indexOf(element))
    }

    //检查是否为空栈
    this.isEmpty = function(){
        return length == 0
    }

    //查询链表长度
    this.size = function(){
        return length
    }

    //获取链表
    this.getHead = function(){
        return head;
    }


}

let l = new LinkedList();