How to Implement a Queue Using JavaScript

A queue is a data structure that follows the First-In-First-Out (FIFO) principle. In JavaScript, arrays can be used to implement various queue operations. Here is a simple example of implementing a queue, including enqueue, dequeue, peek, isEmpty, and size methods:

javascript
class Queue {
    constructor() {
        this.items = [];  // Using an array to store queue elements
    }

    // Enqueue operation
    enqueue(element) {
        this.items.push(element);
    }

    // Dequeue operation
    dequeue() {
        if (this.isEmpty()) {
            return 'Queue is empty';
        }
        return this.items.shift();
    }

    // Peek at the front element
    peek() {
        if (this.isEmpty()) {
            return 'Queue is empty';
        }
        return this.items[0];
    }

    // Check if the queue is empty
    isEmpty() {
        return this.items.length === 0;
    }

    // Get the size of the queue
    size() {
        return this.items.length;
    }
}

// Usage example
const queue = new Queue();
queue.enqueue('John');
queue.enqueue('Jack');
console.log(queue.peek());    // Output: John
queue.dequeue();
console.log(queue.peek());    // Output: Jack
console.log(queue.isEmpty()); // Output: false
console.log(queue.size());    // Output: 1

In this example, we define a Queue class with several methods to simulate queue behavior. The enqueue method adds a new element to the queue, dequeue removes the front element, peek returns the front element without removing it, isEmpty checks if the queue is empty, and size returns the current number of elements in the queue. This implementation uses arrays to simulate typical queue operations as closely as possible.