链表

头指针，总是指向的链表的第一个节点(链表里已有节点),当指针指向的元素并不存在，默认为null（空)。

function LinkedList(){
    /*Node表示链表上的节点,element 代表结点上的元素,next代表姐结点
    里指向下一个结点的指针*/
    var Node = function (element) {
        this.element = element;
        this.next = null;
    }
    //链表的长度
    var length = 0;
    //头指针
    var head = null;
    //在列表尾部添加新项
    this.append = function(element) {
        let node = new Node(element);
        //判断链表头指针是否指向有节点
        if(head === null)
        {
            head = node;
        }
        else
        {
            let current = head;
            while (current.next) {
                 current = current.next;
            }
            current.next = node;
        }
        length++;

    }

    //在链表特定位置移除某一元素
    this.removeAt = function (pos) {
        if(pos > -1 && pos < length){
            let current= head;
            let previous = head;
            let index = 0;
        //移除第一项
        if(pos === 0) {
            head = current.next;
        }
        else {
            while(index++ < pos)
            {
                previous = current;
                current = current.next;
            }
        //将pevious与current的下一项链接起来,跳过current
            previous.next = current.next;
        }
        length--;
        return current.element;
        }
        else {
            return null
        }
    }

    //返回元素在列表中的索引(位置).如果列表中没有该元素则返回-1
    this.indexOf = function (element) {
        let current = head;
        let index = 0;
        
        while(current) {
            if(element === current.element) {
                return index;
            }
            index++;
            current = current.next;
        }
        return -1;
    }
    //链表中移除某一节点
    this.remove = function(element) {
       let index = this.indexOf(element);
       return this.removeAt(index);
    }
    
    //链表元素是否为空
    this.isEmpty = function() {
        return length === 0;
    }

    //返回链表长度
    this.size = function() {
        return length
    }
    
    //链表字符串输出
    this.toString = function () {
        let current = head;
        let string = ;
        while(current) {
            string +=  +current.element;
            current = current.next;
        }
        return  string;
    }
    
}

var linkedList = new LinkedList();
linkedList.append(1);
linkedList.append(2);
linkedList.append(3);
console.log(linkedList.indexOf(3));
linkedList.removeAt(1);
console.log(linkedList.toString());

输出结果如下