JavaScript链表的实现

class Node {                           //结点内部一个next指针一个元素数据
    constructor(element) {
        this.next = null;
        this.element = element;
    }
}
class LinkedList {

    constructor() {                 //链表类属性为一个长度一个头指针
        this.count = 0;
        this.head = null;
    }

    push(element) {

        let node = new Node(element);
        if (this.head == null) {
            this.head = node;

        } else {

            let current = this.head;
            while (current.next != null) {
                current = current.next;
            }
            current.next = node;
        }
        this.count++;

    }

    getElementAt(index) {
        if (index < 0 || index >= this.count) {
            return undefined;
        }
        let current = this.head;   //index===0时不进入循环，返回的current指向head
        for (let i = 0; i < index; i++) {
            current = current.next;
        }
        return current;
    }
    insert(element, index) {
        if (index < 0 || index > this.count) {
            return false;
        }
        let node = new Node(element);
        if (index === 0) {
            node.next = this.head;
            this.head = node;
        } else {
            let current = this.getElementAt(index - 1);
            node.next = current.next;
            current.next = node;
        }
        this.count++;
        return this.count;
    }
    removeAt(index) {
        if (index < 0 || index >= this.count) {
            return undefined;
        }
        let current = this.head;
        if (index === 0) {
            this.head = current.next;
            return current.element;
        }
        let previous = this.getElementAt(index - 1);
        current = previous.next;
        previous.next = current.next;
        this.count--;
        return current.element;

    }
    indexOf(element) {
        let current = this.head;
        for (let i = 0; i < this.count; i++) {
            if (current.element === element) {
                return i;
            }
            current = current.next;
        }
        return -1;
    }
    remove(element) {
        let index = this.indexOf(element);
        return this.removeAt(index);
    }
    isEmpty() {
        return this.count === 0;
    }
    size() {
        return this.count;
    }
    getHead() {
        return this.head;
    }
    clear() {
        this.head = undefined;
        this.count = 0;
    }
    toString() {
        if (this.count === 0) {
            return "";
        }
        let current = this.head;
        let objString = `${current.element}`;
        while (current.next != null) {
            current = current.next;
            objString = `${objString},${current.element}`;
        }
        return objString;
    }
}

//测试用例
let list = new LinkedList();
console.log('push element 15');
list.push(15);

console.log('list.indexOf(15) => ', list.indexOf(15));

console.log('push element 10');
list.push(10);

console.log('list.toString() => ', list.toString());
console.log('list.indexOf(10) => ', list.indexOf(10));

console.log('push element 13');
list.push(13);

console.log('list.toString() => ', list.toString());
console.log('list.indexOf(13) => ', list.indexOf(13));
console.log('list.indexOf(10) => ', list.indexOf(10));

console.log('push elements 11 and 12');
list.push(11);
list.push(12);

console.log('list.toString() => ', list.toString());
console.log('list.removeAt(1) => ', list.removeAt(1));
console.log('list.toString() => ', list.toString());
console.log('list.removeAt(3) => ', list.removeAt(3));
console.log('list.toString() => ', list.toString());

console.log('push element 14');
list.push(14);

console.log('list.toString() => ', list.toString());
console.log('insert element 16 pos 0 => ', list.insert(16, 0));
console.log('list.toString() => ', list.toString());
console.log('insert element 17 pos 1 => ', list.insert(17, 1));
console.log('list.toString() => ', list.toString());
console.log('insert element 18 pos list.size() => ', list.insert(18, list.size()));
console.log('list.toString() => ', list.toString());
console.log('remove element 16 => ', list.remove(16));
console.log('list.toString() => ', list.toString());
console.log('remove element 11 => ', list.remove(11));
console.log('list.toString() => ', list.toString());
console.log('remove element 18 => ', list.remove(18));
console.log('list.toString() => ', list.toString());