What Is Queue in Data Structure W3schools?


Heather Bennett

In data structures, a queue is an abstract data type that follows the FIFO (First-In-First-Out) principle. It is similar to a real-life queue, where the person who arrives first gets served first. In programming, a queue allows you to store and retrieve elements in a specific order.

Operations in Queue

A queue supports two main operations:

  • Enqueue: This operation adds an element to the end of the queue.
  • Dequeue: This operation removes the element from the front of the queue.

Implementation of Queue

A queue can be implemented using various data structures such as arrays or linked lists. Here, we will discuss the implementation using an array:

class Queue {
  constructor() {
    this.items = [];

  enqueue(element) {

  dequeue() {
    if (this.isEmpty()) {
      return "Underflow";
    return this.shift();

  isEmpty() {
    return this.length === 0;

  // Other utility methods

In this implementation, we use an array called this.items to store the elements of the queue. The enqueue() method appends an element to the end of the array, while the dequeue() method removes and returns the first element from the array. The isEmpty() method checks if the queue is empty or not.

Usage of Queue

The concept of queues finds its application in various real-life scenarios and computer algorithms. Some common use cases include:

  • Process Scheduling: Operating systems often use queues to manage the execution of processes.
  • Breadth-First Search: Queues are used in graph traversal algorithms like BFS to explore neighbors level by level.
  • Print Spooling: When multiple print jobs are sent to a printer, they are placed in a queue and processed sequentially.


A queue is a fundamental data structure that follows the FIFO principle. It allows efficient insertion and removal of elements in a specific order. Understanding queues and their implementation is crucial for building efficient algorithms and solving real-world problems.

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