js 数据结构----链表

// 链表
        function LinkedList() {
            var Node = function (element) { // {1}
                this.element = element;
                this.next = null;
            };
            var length = 0; // {2}
            var head = null; // {3}
            // 尾部添加
            this.append = function (element) {
                var node = new Node(element), current;
                if (head === null) {
                    head = Node
                } else {
                    current = head
                    while (current.next) {
                        current = current.next
                    }
                    current.next = node
                }
                length++
            };
            // 指定位置添加
            this.insert = function (position, element) {
                //检查越界值
                if (position >= 0 && position <= length) { //{1}
                    var node = new Node(element),
                        current = head,
                        previous,
                        index = 0;
                    if (position === 0) { //在第一个位置添加 node.next = current; //{2}
                        head = node;
                    } else {
                        while (index++ < position) { //{3}
                            previous = current;
                            current = current.next;
                        }
                        node.next = current; //{4}
                        previous.next = node; //{5}
                    }
                    length++; //更新列表的长度
                    return true;
                } else {
                    return false; //{6}
                }
            };
            // 特定位置移除
            this.removeAt = function (position) {
                //检查越界值
                if (position > -1 && position < length) { // {1}
                    var current = head, // {2}
                        previous, // {3}
                        index = 0; // {4}
                    //移除第一项
                    if (position === 0) { // {5}
                        head = current.next;
                    } else {
                        while (index++ < position) { // {6}
                            previous = current;     // {7}
                            current = current.next; // {8}
                        }
                        //将previous与current的下一项链接起来:跳过current，从而移除它
                        previous.next = current.next; // {9}
                    }
                    length--; // {10}
                    return current.element;
                } else {
                    return null; // {11}
                }
            };
            //移除
            this.remove = function (element) {
                var index = this.indexOf(element);
                return this.removeAt(index);
            };
            //返回元素 在列表中的索引
            this.indexOf = function (element) {
                var current = head, //{1}
                    index = -1;
                while (current) { //{2}
                    if (element === current.element) {
                        return index;       //{3}
                    }
                    index++;                //{4}
                    current = current.next; //{5}
                }
                return -1;
            };
            // 是否为空
            this.isEmpty = function () {
                return length === 0;
            };
            // 元素个数
            this.size = function () {
                return length;
            };

            this.toString = function () {
                var current = head, //{1}
                    string = '';    //{2}
                while (current) {   //{3}
                    string = current.element; //{4}
                    current = current.next;   //{5}
                }
                return string
            };
            this.print = function () { };
            this.getHead = function () {
                return head;
            };
        }