JS data structures - queue

queue.js

'use strict';

function Node(item) {
  this.value = item;
  this.next = null;
}

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

Queue.prototype.queue = function (item) {
  var node = new Node(item);
  if (this.head === null) {
    this.head = node;
    this.tail = node;
  } else {
    this.tail.next = node;
    this.tail = this.tail.next;
  }
};

Queue.prototype.peek = function () {
  if (this.items === null) {
    throw new Error('element does not exist');
  }
  return this.items.value;
};

Queue.prototype.dequeue = function () {
  if (this.head === null) {
    throw new Error('element does not exist');
  }
  var val = this.head.value;
  this.head = this.head.next;
  return val;
};