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https://github.com/datastructures-js/queue
➡️ A performant queue implementation in javascript.
https://github.com/datastructures-js/queue
Last synced: about 2 months ago
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➡️ A performant queue implementation in javascript.
- Host: GitHub
- URL: https://github.com/datastructures-js/queue
- Owner: datastructures-js
- License: mit
- Created: 2018-06-07T00:06:12.000Z (over 6 years ago)
- Default Branch: master
- Last Pushed: 2022-09-05T07:45:14.000Z (about 2 years ago)
- Last Synced: 2024-07-18T19:47:14.932Z (2 months ago)
- Language: JavaScript
- Homepage:
- Size: 65.4 KB
- Stars: 121
- Watchers: 3
- Forks: 9
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Awesome Lists containing this project
README
# @datastructures-js/queue
[](https://www.npmjs.com/package/@datastructures-js/queue)
[](https://www.npmjs.com/packages/@datastructures-js/queue) [](https://www.npmjs.com/package/@datastructures-js/queue)
A performant queue implementation in javascript.
# Contents
* [Install](#install)
* [require](#require)
* [import](#import)
* [API](#api)
* [constructor](#constructor)
* [Queue.fromArray](#queuefromarray)
* [enqueue (push)](#enqueue-push)
* [front](#front)
* [back](#back)
* [dequeue (pop)](#dequeue-pop)
* [isEmpty](#isEmpty)
* [size](#size)
* [clone](#clone)
* [toArray](#toarray)
* [clear](#clear)
* [Build](#build)
* [License](#license)
## Install
```sh
npm install --save @datastructures-js/queue
```
### require
```js
const { Queue } = require('@datastructures-js/queue');
```
### import
```js
import { Queue } from '@datastructures-js/queue';
```
## API
### constructor
##### JS
```js
// empty queue
const queue = new Queue();
// from an array
const queue = new Queue([1, 2, 3]);
```
##### TS
```js
// empty queue
const queue = new Queue();
// from an array
const queue = new Queue([1, 2, 3]);
```
### Queue.fromArray
##### JS
```js
// empty queue
const queue = Queue.fromArray([]);
// with elements
const list = [10, 3, 8, 40, 1];
const queue = Queue.fromArray(list);
// If the list should not be mutated, use a copy of it.
const queue = Queue.fromArray(list.slice());
```
##### TS
```js
// empty queue
const queue = Queue.fromArray([]);
// with elements
const list = [10, 3, 8, 40, 1];
const queue = Queue.fromArray(list);
```
### enqueue (push)
adds an element to the back of the queue.
```js
queue.enqueue(10).enqueue(20); // or queue.push(123)
```
### front
peeks on the front element of the queue.
```js
console.log(queue.front()); // 10
```
### back
peeks on the back element in the queue.
```js
console.log(queue.back()); // 20
```
### dequeue (pop)
removes and returns the front element of the queue in O(1) runtime.
```js
console.log(queue.dequeue()); // 10 // or queue.pop()
console.log(queue.front()); // 20
```
Dequeuing all elements takes O(n) instead of O(n2) when using shift/unshift with arrays.
Explanation by @alexypdu:
Internally, when half the elements have been dequeued, we will resize the dynamic array using `Array.slice()` which runs in $O(n)$. Since dequeuing all $n$ elements will resize the array $\log_2n$ times, the complexity is $$1 + 2 + 4 + \cdots + 2^{\log_2 n - 1} = 2 ^ {(\log_2 n - 1) + 1} - 1 = n - 1 = O(n)$$ Hence the overall complexity of dequeuing all elements is $O(n + n) = O(n)$, and the amortized complexity of `dequeue()` is thus $O(1)$.
benchmark:
dequeuing 1 million elements in Node v14
Queue.dequeueArray.shift
~27 ms~4 mins 31 secs
### isEmpty
checks if the queue is empty.
```js
console.log(queue.isEmpty()); // false
```
### size
returns the number of elements in the queue.
```js
console.log(queue.size()); // 1
```
### clone
creates a shallow copy of the queue.
```js
const queue = Queue.fromArray([{ id: 2 }, { id: 4 } , { id: 8 }]);
const clone = queue.clone();
clone.dequeue();
console.log(queue.front()); // { id: 2 }
console.log(clone.front()); // { id: 4 }
```
### toArray
returns a copy of the remaining elements as an array.
```js
queue.enqueue(4).enqueue(2);
console.log(queue.toArray()); // [20, 4, 2]
```
### clear
clears all elements from the queue.
```js
queue.clear();
queue.size(); // 0
```
### Build
```sh
grunt build
```
## License
The MIT License. Full License is [here](https://github.com/datastructures-js/queue/blob/master/LICENSE)