使链表在ES6中可迭代

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

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

  add(value) {
    const newNode = new Node(value);
    if (!this.head) {
      this.head = newNode;
      this.tail = newNode;
    } else {
      this.tail.next = newNode;
      this.tail = newNode;
    }
  }

  [Symbol.iterator]() {
    let currentNode = this.head;
    return {
      next: () => {
        if (currentNode) {
          const value = currentNode.value;
          currentNode = currentNode.next;
          return { value, done: false };
        } else {
          return { done: true };
        }
      }
    };
  }
}

const list = new LinkedList();
list.add(1);
list.add(2);
list.add(3);

for (const item of list) {
  console.log(item);
}