Now, we'd like to append nodes. Appending is the act of adding to the list. In the event that a linked list does not have a tail reference, we would simply set the value of the last node's next attribute to that of the new node.

However, in this case, we'll just set it to the next of tail, which will always be the last node in the chain.

Note that, as usual, before we set the next value, we need to new up/create a new LinkedListNode that actually contains the actual value.

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append(newVal) {

  const newNode = new LinkedListNode(newVal);

  if (!this.head) {

    this.head = newNode;

    this.tail = newNode;

  } else {

    this.tail.next = newNode;

    this.tail = newNode;

  }

}