JS:DS - Queue Data Structure in JavaScript

The Second Article on the JS:DS series. In this write up we are going to see the Queue Data Structure implementation in javascript and we use arrays for that.

For Stack Data Structure in JS. Please read in the below post.

JS:DS - Stack Data Structure in JavaScript

Saravana Kumar Putta Selvaraj ・ Jun 1 '20 ・ 1 min read

#javascript #datastructure #jsds

What is Queue?

The queue is a data structure to store the data in the order of insertion where the item gets inserted at the first into the queue will be the first one to be removed.

In shorter terms First In First Out(FIFO).

How are we going to implement it?

The following are the methods we are going to have in Queue DS.

initialize — Initialize the storage and queue size
enqueue — push item to the queue
dequeue — remove the first pushed item from the queue
getQueueSize — Get the current queue size

initialize

1. @parmas — size — Queue Size
2. storage — an array to store the items of the queue DS
3. currentQueueSize — to track the size of the queue
4. queueSize — application users can set the predefined size of the queue

class Queue {
  constructor(size) {
    this.storage = [];
    this.currentqueueSize = 0;
    this.queueSize = size ? size : 10;
  }
}

enqueue - Add items to the queue

1. Check the current size of the queue is less than the actual queue size.
2. If the above condition gets a pass, increase the current queue size by 1, and push the item to the Queue.
3. Else throw the error saying that the queue is full!

class Queue {
  constructor(size) {
    this.storage = [];
    this.currentqueueSize = 0;
    this.queueSize = size ? size : 10;
  }
  enqueue(item) {
    if (this.currentqueueSize < this.queueSize) {
      this.queueSize++;
      this.storage.push(item);
    } else {
      throw 'Cannot enqueu. Since the Queue is full!'
    }
  }
}

dequeue - Remove items from the queue

1. Check the current size of the queue is greater than 0.
2. If the above condition gets a pass, decrease the current queue size by 1, and remove the item from the first position in an array using shift().
3. Else throw the error saying that the queue is empty!

class Queue {
  constructor(size) {
    this.storage = [];
    this.currentqueueSize = 0;
    this.queueSize = size ? size : 10;
  }
  dequeue() {
    if (this.currentqueueSize > 0) {
      this.currentqueueSize--;
      return this.storage.shift();
    }
    throw 'Cannot dequeue. Since the Queue is empty!'
  }
}

getQueueSize

Return the current Queue size from the initialization part

class Queue {
  constructor(size) {
    this.storage = [];
    this.currentqueueSize = 0;
    this.queueSize = size ? size : 10;
  }
  getQueueSize() {
    return this.currentqueueSize;
  }
}

Complete code in below gist

	class Queue {
	/*
	Initialization
	@parmas - size - Queue Size
	storage - an array to store the items of the queue DS
	currentQueueSize - to track the size of the queue
	queueSize - application users can set the predefined size for the queue
	*/
	constructor(size) {
	this.storage = [];
	this.currentqueueSize = 0;
	this.queueSize = size ? size : 10;
	}
	/*
	enqueue - Add items to the queue
	1. Check the current size of the queue is less than the actual queue size.
	2. If above condition gets pass, increase the current queue size by 1 and push the item to queue.
	3. Else throw the error saying that the queue is full!
	*/
	enqueue(item) {
	if (this.currentqueueSize < this.queueSize) {
	this.queueSize++;
	this.storage.push(item);
	} else {
	throw 'Cannot enqueu. Since the Queue is full!'
	}
	}
	/*
	dequeue - Remove items from the queue
	1. Check the current size of the queue is greater than 0.
	2. If above condition gets pass, decrease the current queue size by 1 and remove the item from the first position in array using shift().
	3. Else throw the error saying that the queue is empty!
	*/
	dequeue() {
	if (this.currentqueueSize > 0) {
	this.currentqueueSize--;
	return this.storage.shift();
	}
	throw 'Cannot dequeue. Since the Queue is empty!'
	}
	/*
	getQueueSize - return the current queue size
	*/
	getQueueSize() {
	return this.currentqueueSize;
	}
	}
	let queue1 = new Queue(10);
	/* Access queue methods as
	queue1.enqueue(item),
	queue1.dequeue()
	queue1.getQueueSize()
	*/
	console.log(queue1);

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