How to implement deque data structure in javascript?

Implementing a deque (double-ended queue) data structure in JavaScript can be achieved by using an array to simulate a data structure that supports insertion and deletion at both ends. Here's how to implement the basic functionality of a deque in JavaScript:

Defining the Deque Class

First, we define a Deque class that contains an internal array to store elements and provides methods for operating on these elements.

javascript
class Deque {
    constructor() {
        this.items = [];
    }

    // Add element to the front of the deque
    addFront(element) {
        this.items.unshift(element);
    }

    // Add element to the back of the deque
    addBack(element) {
        this.items.push(element);
    }

    // Remove element from the front of the deque
    removeFront() {
        if (this.isEmpty()) {
            return undefined;
        }
        return this.items.shift();
    }

    // Remove element from the back of the deque
    removeBack() {
        if (this.isEmpty()) {
            return undefined;
        }
        return this.items.pop();
    }

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

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

    // Clear the deque
    clear() {
        this.items = [];
    }

    // View the front element
    front() {
        if (this.isEmpty()) {
            return undefined;
        }
        return this.items[0];
    }

    // View the back element
    back() {
        if (this.isEmpty()) {
            return undefined;
        }
        return this.items[this.items.length - 1];
    }
}

Usage Example

Here are some examples of using the Deque class:

javascript
let deque = new Deque();

// Add elements
deque.addBack(1);
deque.addBack(2);
deque.addFront(0);
console.log(deque.items);  // [0, 1, 2]

// Remove elements
console.log(deque.removeFront());  // 0
console.log(deque.removeBack());   // 2
console.log(deque.items);  // [1]

// Check functionality
console.log(deque.isEmpty());  // false
console.log(deque.size());  // 1
console.log(deque.front());  // 1
console.log(deque.back());  // 1

// Clear the deque
deque.clear();
console.log(deque.isEmpty());  // true

In this implementation, we leverage JavaScript array methods push, pop, shift, and unshift to simplify the implementation of addBack, removeBack, removeFront, and addFront, which respectively handle adding and removing elements from the end and beginning of the array.