alternateQueue.js

/**
 * Alternate Queue Combination
 * @author MadhavBahl
 * @date 15/02/2019
 */

class Queue {
    constructor (size) {
        this.capacty = size;
        this.data = [];
        this.frontIndex = 0;
        this.rearIndex = 0;
    }

    front () {
        return data[this.frontIndex];
    }

    rear () {
        return data[this.rearIndex];
    }

    enqueue (element) {
        if (this.rearIndex >= this.capacty)  {
            console.log ("Overflow!");
            return -1;
        }
        this.data.unshift (element);
        // console.log (element + ' added to the queue');
        this.rearIndex++;
    }

    dequeue (element) {
        if (this.rearIndex === 0) {
            console.log ("Underflow!");
            return -1;
        }
        // console.log (this.data[this.rearIndex -1] + ' has been removed from the queue');
        this.rearIndex--;
        return this.data.pop ();
    }

    displayQueue () {
        let toBeDisplayed = '-> ';
        for (let element of this.data) {
            toBeDisplayed += element + ' -> ';
        }
        console.log (toBeDisplayed);
    }
}

const combine = (q1, q2) => {
    let toBeAdded;
    const combinedQueue = new Queue (q1.rearIndex + q2.rearIndex);
    while (!(q1.rearIndex === 0 || q2.rearIndex === 0)) {
        toBeAdded = q1.dequeue();
        combinedQueue.enqueue (toBeAdded);
        toBeAdded = q2.dequeue();
        combinedQueue.enqueue (toBeAdded);
    }
    console.log ("\n/* ===== Displaying Combined Queue ===== */");
    combinedQueue.displayQueue();
}

const firstQ = new Queue (4);

firstQ.enqueue (1);
firstQ.enqueue (2);
firstQ.enqueue (3);
firstQ.enqueue (4);

const secondQ = new Queue (4);

secondQ.enqueue (5);
secondQ.enqueue (6);
secondQ.enqueue (7);
secondQ.enqueue (8);

console.log ("\n/* ===== Displaying Queue 1 ===== */");
firstQ.displayQueue();
console.log ("\n/* ===== Displaying Queue 2 ===== */");
secondQ.displayQueue();

combine (firstQ, secondQ);