queue-list

👉Note: All methods including enqueue, dequeue, peek, isEmpty, size, and clear have constant time complexity 😎 O(1)

queue-list is a JavaScript library for managing a queue data structure. It provides a simple and efficient way to handle elements in a queue with various methods for manipulating and querying the queue. The library also customizes console.log to format Queue instances.

Installation

To install queue-list, use npm:

npm install queue-list

Importing

import Queue from 'queue-list';

Methods

Method	Purpose	Returns	Time Complexity	Example Use Case
enqueue	Adds a new element to the end of the queue.	The queue instance (this)	O(1)	queue.enqueue(1).enqueue('text').enqueue({ key: 'value' });
dequeue	Removes and returns the element at the front of the queue.	The removed element or null if empty	O(1)	const value = queue.dequeue(); // 1
peek	Returns the value of the front element without removing it.	The front element or null if empty	O(1)	const front = queue.peek(); // 'text'
isEmpty	Checks if the queue is empty.	true if empty, false otherwise	O(1)	const empty = queue.isEmpty(); // false
size	Returns the number of elements in the queue.	The number of elements	O(1)	const length = queue.size(); // 2
clear	Removes all elements from the queue and resets it to an empty state.	The queue instance (this)	O(1)	queue.clear();
toArray	Converts the queue to an array of elements.	An array of elements	O(n)	const array = queue.toArray(); // [1, 'text', '{"key":"value"}']
getType	Returns the type of data structure.	"queue"	O(1)	const type = queue.getType(); // "queue"

Custom Console Logging

The console.log method has been customized to properly handle and format Queue instances. When logging a Queue instance, its toString representation will be used.

Example

import Queue from 'queue-list';

const queue = new Queue(10, "text", { key: 'value' });

console.log(queue); // Output: Front -> |10| |"text"| |{"key":"value"}| <- Rear

queue.dequeue();
console.log(queue); // Output: Front -> |"text"| |{"key":"value"}| <- Rear

queue.clear();
console.log(queue); // Output: Front -> || <- Rear

Detailed Example Use Cases

enqueue(value)

Purpose: Adds a new element to the end of the queue.

Typical Use Case:

import Queue from 'queue-list';

const queue = new Queue(1, "string", true, [1, 2], { key: 'value' });
queue.enqueue(null).enqueue(undefined);
console.log(queue); // Output: "Front -> |1| |"string"| |true| |[1,2]| |{"key":"value"}| |null| |undefined| <- Rear"

Edge Cases:

1. Enqueue on an empty queue:

const queue = new Queue();
queue.enqueue(10).enqueue("text").enqueue([1, 2, 3]).enqueue({ key: 'value' });
console.log(queue); // Output: "Front -> |10| |"text"| |[1,2,3]| |{"key":"value"}| <- Rear"

2. Enqueue on a non-empty queue:

const queue = new Queue('initial');
queue.enqueue(42).enqueue({ foo: 'bar' }).enqueue([1, 2]);
console.log(queue); // Output: "Front -> |'initial'| |42| |{"foo":"bar"}| |[1,2]| <- Rear"

dequeue()

Purpose: Removes and returns the element at the front of the queue. Returns null if the queue is empty.

Typical Use Case:

import Queue from 'queue-list';

const queue = new Queue(1, 'text', { key: 'value' });
console.log(queue.dequeue()); // Output: 1
console.log(queue); // Output: "Front -> |'text'| |{"key":"value"}| <- Rear"

Edge Cases:

1. Dequeue from an empty queue:

const queue = new Queue();
console.log(queue.dequeue()); // Output: null

2. Dequeue until the queue is empty:

const queue = new Queue('item1', 'item2');
console.log(queue.dequeue()); // Output: 'item1'
console.log(queue.dequeue()); // Output: 'item2'
console.log(queue.dequeue()); // Output: null

peek()

Purpose: Returns the value of the front element without removing it. Returns null if the queue is empty.

Typical Use Case:

import Queue from 'queue-list';

const queue = new Queue('first', 42, { key: 'value' });
console.log(queue.peek()); // Output: 'first'

Edge Cases:

1. Peek on an empty queue:

const queue = new Queue();
console.log(queue.peek()); // Output: null

2. Peek after several enqueues and dequeues:

const queue = new Queue('item1', 'item2', 'item3');
queue.dequeue(); // Removes 'item1'
console.log(queue.peek()); // Output: 'item2'

isEmpty()

Purpose: Checks if the queue is empty.

Typical Use Case:

import Queue from 'queue-list';

const queue = new Queue(1, 'text');
console.log(queue.isEmpty()); // Output: false
queue.dequeue();
queue.dequeue();
console.log(queue.isEmpty()); // Output: true

Edge Cases:

1. Check if an empty queue is empty:

const queue = new Queue();
console.log(queue.isEmpty()); // Output: true

2. Check after adding and removing elements:

const queue = new Queue();
queue.enqueue('data');
console.log(queue.isEmpty()); // Output: false
queue.dequeue();
console.log(queue.isEmpty()); // Output: true

size()

Purpose: Returns the number of elements in the queue.

Typical Use Case:

import Queue from 'queue-list';

const queue = new Queue(1, 'text', [1, 2], { key: 'value' });
console.log(queue.size()); // Output: 4

Edge Cases:

1. Size of an empty queue:

const queue = new Queue();
console.log(queue.size()); // Output: 0

2. Size after several operations:

const queue = new Queue('start');
queue.enqueue('middle');
queue.dequeue();
console.log(queue.size()); // Output: 1

clear()

Purpose: Removes all elements from the queue and resets it to an empty state.

Typical Use Case:

import Queue from 'queue-list';

const queue = new Queue(1, 'text', [1, 2]);
queue.clear();
console.log(queue); // Output: "Front -> || <- Rear"
console.log(queue.isEmpty()); // Output: true

Edge Cases:

1. Clear an empty queue:

const queue = new Queue();
queue.clear();
console.log(queue); // Output: "Front -> || <- Rear"

2. Clear a queue with elements:

const queue = new Queue('item1', 'item2');
queue.clear();
console.log(queue.size()); // Output: 0

toArray()

Purpose: Converts the queue to an array of elements.

Typical Use Case:

import Queue from 'queue-list';

const queue = new Queue(1, 'text', [1, 2], { key: 'value' });
console.log(queue.toArray()); // Output: [1, 'text', [1,2], {"key":"value"}]

Edge Cases:

1. Convert an empty queue to an array:

const queue = new Queue();
console.log(queue.toArray()); // Output: []

2. Convert a queue with various elements:

const queue = new Queue('string', 42, { foo: 'bar' }, [1, 2]);
console.log(queue.toArray()); // Output: [ 'string', 42, { foo: 'bar' }, [ 1, 2 ] ]

getType()

Purpose: Returns the type of data structure.

Typical Use Case:

import Queue from 'queue-list';

const queue = new Queue();
console.log(queue.getType()); // Output: "queue"

Edge Cases:

1. Type of an empty queue:

const queue = new Queue();
console.log(queue.getType()); // Output: "queue"

2. Type after various operations:

const queue = new Queue();
queue.enqueue('element');
console.log(queue.getType()); // Output: "queue"

License

This project is licensed under the MIT License - see the LICENSE.md file for details.

Acknowledgments

This package is inspired by the need for a simple and efficient queue implementation in JavaScript. Feel free to use and contribute to make this package even better! If you encounter any issues or have suggestions for improvement, please open an issue on the GitHub repository.

Here is the GitHub Repo Link.