LinkedListStarter.js

class ListNode {
  /**
   * Create a new node
   * @param {*} value The value to assign to the linked list.
   * @param {ListNode | null} next  The pointer to the next node in the chain
   */
  constructor(value, next = null) {
    // The value of the node.  Can  be anything.
    this.value = value;
    // the pointer to the next node in the chain.
    this.next = next;
  }
}

class LinkedList {
  /**
   * Create a new Linked List
   */
  constructor() {
    // Size of the  linked list
    this.size = 0;
    // a pointer to the first node
    this.head = null;
    // a pointer to the last node.
    this.tail = null;
  }

  /**
   * Add a value to teh beginning of the linked list.
   * @param {*} value The value to assign to the linked list.
   * @returns {LinkedList}
   */
  prepend(value) {
    // create a new node in memory
    // Make it's  'next' point to the memory address currently in this.head.
    // currently at this.head.
    const node = new ListNode(value, this.head);

    // set this.head to the address of the new node.
    this.head = node;

    // If there is no tail (if this is the first entry)
    // set this.tail to point to the memory address for node.
    if (!this.tail) this.tail = node;

    // inc sizr
    this.size++;

    // return 'this' so we can chain multiple
    return this;
  }

  /**
   * Add a value to the end of the linked list.
   * @param {*} value The value to add 
   * @returns {LinkedList}
   */
  append(value) {
    // Create a mew mpde in memory
    const node = new ListNode(value);

    // If there are no nodes, make a the pinters to our new node, 
    if (this.size === 0) {
      this.head = node;
      this.tail = node;
    } else {
      // else if there already nodes in the list
      // set the next value in the node currently in this.tail.
      this.tail.next = node;

      // Set the tail pointer to the address of the new node.
      this.tail = node;
    }

    // Increase the list size
    this.size++;
    return this;
  }

  /**
   * Print details about the linked list
   */
  print() {
    console.log("HEAD:", this.head);
    console.log("TAIL:", this.tail);
    console.log("SIZE:", this.size);
    console.log(JSON.stringify(this, null, 2));
  }
}

// instantiate the new class
const list = new LinkedList();

// write some tests!!