Linked List implementation of a queue

Queue.js

function LinkNode(value, prev = null, next = null) {
  this.value = value;
  this.prev = prev;
  this.next = next;
}

function Queue() {
  this.head = null;
  this.tail = null;

  this.isEmpty = function isEmpty() {
    return this.head === null;
  };

  this.push = function push(value) {
    const newNode = new LinkNode(value);
    if (this.isEmpty()) {
      this.head = newNode;
      this.tail = newNode;
    } else  {
      newNode.next = this.head;
      this.head.prev = newNode;
      this.head = newNode;
    }

    return this.head;
  };

  this.pop = function pop() {
    if (this.isEmpty()) {
      return null;
    }
    const tailNode = this.tail;

    if (tailNode === this.head) {
      this.head = this.tail = null;
      return tailNode.value;
    }

    this.tail = tailNode.prev;
    tailNode.prev = null;
    this.tail.next = null;

    return tailNode.value;
  };
}

const q = new Queue();

q.push(1);
q.push(2);
q.push(3);
q.push(4);
q.push(5);

q.pop();
q.pop();
q.pop();
q.pop();
q.pop();
q.pop();