Welcome to the practical segment of our JavaScript programming journey! Today, we're applying the knowledge from past lessons to solve two practice problems using advanced JavaScript data structures: queues, deques, and binary search trees with custom class keys.

Consider an event-driven system, like a restaurant. Orders arrive, and they must be handled in the order they were received, following the First In, First Out (FIFO) principle. This principle makes it a perfect scenario for a queue or deque implementation in JavaScript.

This code demonstrates the creation and operation of a class, which leverages JavaScript arrays to efficiently implement a queue. The class includes methods to (add) an item, (remove) an item, check if the queue is empty, and return the queue's size. Enqueue operations add an item to the beginning of the array (simulating the arrival of a new order), while dequeue operations remove an item from the end (simulating the serving of an order), maintaining the principle.