priorityqueue.js

//https://www.geeksforgeeks.org/implementation-priority-queue-javascript/amp/

// User defined class
// to store element and its priority
class QElement {
    constructor(element, priority) {
        this.element = element;
        this.priority = priority;
    }
}


// PriorityQueue class
class PriorityQueue {

    // An array is used to implement priority
    constructor() {
        this.items = [];
    }

    // enqueue function to add element
    // to the queue as per priority
    enqueue(element, priority) {

        // creating object from queue element
        var qElement = new QElement(element, priority);
        var contain = false;

        // iterating through the entire
        // item array to add element at the
        // correct location of the Queue
        for (var n = 0; n < this.items.length; n++) {
            if (this.items[n].priority > qElement.priority) {
                // Once the correct location is found it is
                // enqueued
                this.items.splice(n, 0, qElement);
                contain = true;
                break;
            }
        }

        // if the element have the highest priority
        // it is added at the end of the queue
        if (!contain) {
            this.items.push(qElement);
        }
    }

    // dequeue method to remove
    // element from the queue
    dequeue() {
        // return the dequeued element
        // and remove it.
        // if the queue is empty
        // returns Underflow
        if (this.isEmpty()) return "Underflow";
        return this.items.shift();
    }

    // front function
    front() {
        // returns the highest priority element
        // in the Priority queue without removing it.
        if (this.isEmpty()) return "No elements in Queue";
        return this.items[0];
    }

    // rear function
    rear() {
        // returns the lowest priorty
        // element of the queue
        if (this.isEmpty()) return "No elements in Queue";
        return this.items[this.items.length - 1];
    }

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

    // printQueue function
    // prints all the element of the queue
    printPQueue() {
        var str = "";
        for (var n = 0; n < this.items.length; n++)
            str += this.items[n].element + " ";
        return str;
    }
}


//---------------
// creating object for queue classs

var priorityQueue = new PriorityQueue();
// testing isEmpty and front on an empty queue
// return true
console.log(priorityQueue.isEmpty());
// returns "No elements in Queue"
console.log(priorityQueue.front());
// adding elements to the queue
priorityQueue.enqueue("Sumit", 2);
priorityQueue.enqueue("Gourav", 1);
priorityQueue.enqueue("Piyush", 1);
priorityQueue.enqueue("Sunny", 2);
priorityQueue.enqueue("Sheru", 3);
// prints [Gourav Piyush Sumit Sunny Sheru]
console.log(priorityQueue.printPQueue());
// prints Gourav
console.log(priorityQueue.front().element);
// pritns Sheru
console.log(priorityQueue.rear().element);
// removes Gouurav
// priorityQueue contains
// [Piyush Sumit Sunny Sheru]
console.log(priorityQueue.dequeue().element);
// Adding another element to the queue
priorityQueue.enqueue("Sunil", 2);
// prints [Piyush Sumit Sunny Sunil Sheru]
console.log(priorityQueue.printPQueue());