Init

.editorconfig

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+root = true
+
+[*]
+indent_style = tab
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.yml]
+indent_style = space
+indent_size = 2

.gitattributes

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+* text=auto eol=lf

.github/funding.yml

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+github: sindresorhus
+open_collective: sindresorhus
+custom: https://sindresorhus.com/donate

.github/workflows/main.yml

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+name: CI
+on:
+  - push
+  - pull_request
+jobs:
+  test:
+    name: Node.js ${{ matrix.node-version }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        node-version:
+          - 14
+          - 12
+          - 10
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v1
+        with:
+          node-version: ${{ matrix.node-version }}
+      - run: npm install
+      - run: npm test

.gitignore

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+node_modules
+yarn.lock

.npmrc

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+package-lock=false

index.d.ts

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+declare class Queue<ValueType> implements Iterable<ValueType> {
+	/**
+	The size of the queue.
+	*/
+	readonly size: number;
+
+	/**
+	Tiny queue data structure.
+
+	The instance is an [`Iterable`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols), which means you can iterate over the queue front to back with a “for…of” loop, or use spreading to convert the queue to an array. Don't do this unless you really need to though, since it's slow.
+
+	@example
+	```
+	import Queue = require('yocto-queue');
+
+	const queue = new Queue();
+
+	queue.enqueue('🦄');
+	queue.enqueue('🌈');
+
+	console.log(queue.size);
+	//=> 2
+
+	console.log(...queue);
+	//=> '🦄 🌈'
+
+	console.log(queue.dequeue());
+	//=> '🦄'
+
+	console.log(queue.dequeue());
+	//=> '🌈'
+	```
+	*/
+	constructor();
+
+	[Symbol.iterator](): IterableIterator<ValueType>;
+
+	/**
+	Add a value to the queue.
+	*/
+	enqueue(value: ValueType): void;
+
+	/**
+	Remove the next value in the queue.
+
+	@returns The removed value or `undefined` if the queue is empty.
+	*/
+	dequeue(): ValueType | undefined;
+
+	/**
+	Clear the queue.
+	*/
+	clear(): void;
+}
+
+export = Queue;

index.js

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+class Node {
+	/// value;
+	/// next;
+
+	constructor(value) {
+		this.value = value;
+
+		// TODO: Remove this when targeting Node.js 12.
+		this.next = undefined;
+	}
+}
+
+class Queue {
+	// TODO: Use private class fields when targeting Node.js 12.
+	// #_head;
+	// #_tail;
+	// #_size;
+
+	constructor() {
+		this.clear();
+	}
+
+	enqueue(value) {
+		const node = new Node(value);
+
+		if (this._head) {
+			this._tail.next = node;
+			this._tail = node;
+		} else {
+			this._head = node;
+			this._tail = node;
+		}
+
+		this._size++;
+	}
+
+	dequeue() {
+		const current = this._head;
+		if (!current) {
+			return;
+		}
+
+		this._head = this._head.next;
+		this._size--;
+		return current.value;
+	}
+
+	clear() {
+		this._head = undefined;
+		this._tail = undefined;
+		this._size = 0;
+	}
+
+	get size() {
+		return this._size;
+	}
+
+	* [Symbol.iterator]() {
+		let current = this._head;
+
+		while (current) {
+			yield current.value;
+			current = current.next;
+		}
+	}
+}
+
+module.exports = Queue;

index.test-d.ts

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+import {expectType} from 'tsd';
+import Queue = require('.');
+
+const queue = new Queue<string>();
+queue.enqueue('🦄');
+
+expectType<string | undefined>(queue.dequeue());

license

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+MIT License
+
+Copyright (c) Sindre Sorhus <[email protected]> (https://sindresorhus.com)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

package.json

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+{
+	"name": "yocto-queue",
+	"version": "0.0.0",
+	"description": "Tiny queue data structure",
+	"license": "MIT",
+	"repository": "sindresorhus/yocto-queue",
+	"funding": "https://github.com/sponsors/sindresorhus",
+	"author": {
+		"name": "Sindre Sorhus",
+		"email": "[email protected]",
+		"url": "https://sindresorhus.com"
+	},
+	"engines": {
+		"node": ">=10"
+	},
+	"scripts": {
+		"test": "xo && ava && tsd"
+	},
+	"files": [
+		"index.js",
+		"index.d.ts"
+	],
+	"keywords": [
+		"queue",
+		"data",
+		"structure",
+		"algorithm",
+		"queues",
+		"queuing",
+		"list",
+		"array",
+		"linkedlist",
+		"fifo",
+		"enqueue",
+		"dequeue",
+		"data-structure"
+	],
+	"devDependencies": {
+		"ava": "^2.4.0",
+		"tsd": "^0.13.1",
+		"xo": "^0.35.0"
+	}
+}

readme.md

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+# yocto-queue [![](https://badgen.net/bundlephobia/minzip/yocto-queue)](https://bundlephobia.com/result?p=yocto-queue)
+
+> Tiny queue data structure
+
+You should use this package instead of an array if you do a lot of `Array#push()` and `Array#shift()` on large arrays, since `Array#shift()` has [linear time complexity](https://medium.com/@ariel.salem1989/an-easy-to-use-guide-to-big-o-time-complexity-5dcf4be8a444#:~:text=O(N)%E2%80%94Linear%20Time) *O(n)* while `Queue#dequeue()` has [constant time complexity](https://medium.com/@ariel.salem1989/an-easy-to-use-guide-to-big-o-time-complexity-5dcf4be8a444#:~:text=O(1)%20%E2%80%94%20Constant%20Time) *O(1)*. That makes a huge difference for large arrays.
+
+> A [queue](https://en.wikipedia.org/wiki/Queue_(abstract_data_type)) is an ordered list of elements where an element is inserted at the end of the queue and is removed from the front of the queue. A queue works based on the first-in, first-out ([FIFO](https://en.wikipedia.org/wiki/FIFO_(computing_and_electronics))) principle.
+
+## Install
+
+```
+$ npm install yocto-queue
+```
+
+## Usage
+
+```js
+const Queue = require('yocto-queue');
+
+const queue = new Queue();
+
+queue.enqueue('🦄');
+queue.enqueue('🌈');
+
+console.log(queue.size);
+//=> 2
+
+console.log(...queue);
+//=> '🦄 🌈'
+
+console.log(queue.dequeue());
+//=> '🦄'
+
+console.log(queue.dequeue());
+//=> '🌈'
+```
+
+## API
+
+### `queue = new Queue()`
+
+The instance is an [`Iterable`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols), which means you can iterate over the queue front to back with a “for…of” loop, or use spreading to convert the queue to an array. Don't do this unless you really need to though, since it's slow.
+
+#### `.enqueue(value)`
+
+Add a value to the queue.
+
+#### `.dequeue()`
+
+Remove the next value in the queue.
+
+Returns the removed value or `undefined` if the queue is empty.
+
+#### `.clear()`
+
+Clear the queue.
+
+#### `.size`
+
+The size of the queue.
+
+## Related
+
+- [quick-lru](https://github.com/sindresorhus/quick-lru) - Simple “Least Recently Used” (LRU) cache

test.js

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+import test from 'ava';
+import Queue from '.';
+
+test('.enqueue()', t => {
+	const queue = new Queue();
+	queue.enqueue('🦄');
+	t.is(queue.dequeue(), '🦄');
+	queue.enqueue('🌈');
+	queue.enqueue('❤️');
+	t.is(queue.dequeue(), '🌈');
+	t.is(queue.dequeue(), '❤️');
+});
+
+test('.dequeue()', t => {
+	const queue = new Queue();
+	t.is(queue.dequeue(), undefined);
+	t.is(queue.dequeue(), undefined);
+	queue.enqueue('🦄');
+	t.is(queue.dequeue(), '🦄');
+	t.is(queue.dequeue(), undefined);
+});
+
+test('.clear()', t => {
+	const queue = new Queue();
+	queue.clear();
+	queue.enqueue(1);
+	queue.clear();
+	t.is(queue.size, 0);
+	queue.enqueue(1);
+	queue.enqueue(2);
+	queue.enqueue(3);
+	queue.clear();
+	t.is(queue.size, 0);
+});
+
+test('.size', t => {
+	const queue = new Queue();
+	t.is(queue.size, 0);
+	queue.clear();
+	t.is(queue.size, 0);
+	queue.enqueue('🦄');
+	t.is(queue.size, 1);
+	queue.enqueue('🦄');
+	t.is(queue.size, 2);
+	queue.dequeue();
+	t.is(queue.size, 1);
+	queue.dequeue();
+	t.is(queue.size, 0);
+	queue.dequeue();
+	t.is(queue.size, 0);
+});
+
+test('iterable', t => {
+	const queue = new Queue();
+	queue.enqueue('🦄');
+	queue.enqueue('🌈');
+	t.deepEqual([...queue], ['🦄', '🌈']);
+});