LinkedList.js

class LinkList {
  constructor(value) {
    this._head = { value, next: null };
    this._tail = this._head;
  }

  insert(value) {
    //update tail as needed
    const node = { value, next: null };
    this._tail.next = node;
    this._tail = node;
  }

  removeTail() {
    let currentNode = this._head;
    // if we reach the 2nd last node stop
    while (currentNode.next != this._tail) {
      // we assign the next to the currentNode
      currentNode = currentNode.next;
    }
    // reset next node to null
    currentNode.next = null;
    // tail is now the 2nd latest node
    this._tail = currentNode;
  }

  isHead() {}
  isTail() {}
}