class Node {
    constructor(value) {
      this.value = value;
      this.next = null;
    }
  }
  
  class LinkedList {
    constructor() {
      this.head = null;
      this.tail = null;
      this.length = 0;
    }
  
    append(value) {
      const newNode = new Node(value);
      if (!this.head) {
        this.head = newNode;
        this.tail = newNode;
      } else {
        this.tail.next = newNode;
        this.tail = newNode;
      }
      this.length++;
    }
  }
  
  const list = new LinkedList();
  list.append(1);
  list.append(2);
  list.append(3);