doubly_linked.js

class Node {
    constructor(data) {
        this.data = data;
        this.next = null;
        this.prev = null;
    }
}

class DoublyLinkedList {
    constructor() {
        this.head = null;
    }

    append(data) {
        const newNode = new Node(data);
        if (this.head === null) {
            this.head = newNode;
            return;
        }
        let last = this.head;
        while (last.next !== null) {
            last = last.next;
        }
        last.next = newNode;
        newNode.prev = last;
    }

    printList() {
        let current = this.head;
        let result = '';
        while (current !== null) {
            result += current.data + ' <-> ';
            current = current.next;
        }
        console.log(result + 'NULL');
    }
}

const list = new DoublyLinkedList();
list.append(1);
list.append(2);
list.append(3);
list.printList(); // 输出：1 <-> 2 <-> 3 <-> NULL

/*
jarry@MacBook-Pro linked % node doubly_linked.js
1 <-> 2 <-> 3 <-> NULL
*/