The fastest javascript implementation of a double-ended queue. Maintains compatability with deque. 

The fastest javascript implementation of a double-ended queue. Used by the official Redis, MongoDB, MariaDB & MySQL libraries for Node.js and many other libraries. Maintains compatability with deque.

salakar

denque

The fastest javascript implementation of a double-ended queue. Maintains compatability with deque.

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 * Custom implementation of a double ended queue.

 * This is almost double the performance of petkaantonov's double-ended-queue lib. ¯\_(ツ)_/¯

   * Returns the item at the specified index from the list.

   * 0 is the first element, 1 is the second, and so on...

   * Elements at negative values are that many from the end: -1 is one before the end

   * (the last element), -2 is two before the end (one before last), etc.

    // expect a number or return undefined

    if (i >= len || i < -len) return undefined;

    i = (this._head + i) & this._capacityMask;

   * Returns the first item in the list without removing it.

    if (this._head === this._tail) return undefined;

   * Returns the item that is at the back of the queue without removing it.

   * Returns the current length of the queue

   * Return the number of items on the list, or 0 if empty.

    if (this._head === this._tail) return 0;

    if (this._head < this._tail) return this._tail - this._head;

    else return this._capacityMask + 1 - (this._head - this._tail);

   * Add an item at the beginning of the list.

    if (item === undefined) return this.length;

  "description": "The fastest javascript implementation of a double-ended queue. Maintains compatability with deque.",

    "test": "istanbul cover --report lcov _mocha",

    "coveralls": "cat ./coverage/lcov.info | coveralls",

    "benchmark_thousand": "node benchmark/thousand",

    "benchmark_two_million": "node benchmark/two_million"

    "url": "git+https://github.com/Salakar/denque.git"

    "url": "https://github.com/Salakar/denque/issues"

  "homepage": "https://github.com/Salakar/denque#readme",

[![Coverage Status](https://coveralls.io/repos/github/Salakar/denque/badge.svg?branch=master)](https://coveralls.io/github/Salakar/denque?branch=master)

[![dependencies](https://img.shields.io/david/Salakar/denque.svg)](https://david-dm.org/Salakar/denque)

[![build](https://travis-ci.org/Salakar/denque.svg)](https://travis-ci.org/Salakar/denque)

[![npm version](https://img.shields.io/npm/v/denque.svg)](https://www.npmjs.com/package/denque)

[![License](https://img.shields.io/npm/l/denque.svg)](/LICENSE)

Extremely fast [double-ended queue](http://en.wikipedia.org/wiki/Double-ended_queue) implementation. Double-ended queues can also be used as a:

Extremely fast and lightweight [double-ended queue](http://en.wikipedia.org/wiki/Double-ended_queue) implementation with zero dependencies.

Double-ended queues can also be used as a:

- [Stack](http://en.wikipedia.org/wiki/Stack_\(abstract_data_type\))

- [Queue](http://en.wikipedia.org/wiki/Queue_\(data_structure\))

This implementation is currently the fastest available, even faster than `double-ended-queue`, see the [benchmarks](#benchmarks)

Every queue operation is done at a constant `O(1)` - including random access from `.peekAt(index)`.

**Requires Node.js v4+, io.js v3+** or any platform supporting ES6 classes (pretty much all browsers).

- [`new Denque(Array items)`](#new-denquearray-items---denque)

- [`peekAt(int index)`](#peekAtint-index---dynamic)

Creates an empty double-ended queue with initial capacity of 4.

#####`new Denque(Array items)` -> `Denque`

Creates a double-ended queue from `items`.

Push an item to the back of this queue. Returns the amount of items currently in the queue after the operation.

Unshift an item to the front of this queue. Returns the amount of items currently in the queue after the operation.

Pop off the item at the back of this queue.

Note: The item will be removed from the queue. If you simply want to see what's at the back of the queue use [`peekBack()`](#peekback---dynamic) or [`.peekAt(-1)`](#peekAtint-index---dynamic).

If the queue is empty, `undefined` is returned. If you need to differentiate between `undefined` values in the queue and `pop()` return value -

check the queue `.length` before popping.

describe('Denque.prototype.constructor', function () {

  it("should take no argument", function () {

  it("should take array argument", function () {

    assert.deepEqual(a.toArray(), [1, 2, 3, 4]);

  it("should handle a high volume with no out of memory exception", function () {

describe('Denque.prototype.toArray', function () {

  it("should return an array", function () {

describe('Denque.prototype.push', function () {

  it("Should do nothing if no arguments", function () {

  it("Should add falsey elements (except undefined)", function () {

  it("Should add single argument - plenty of capacity", function () {

    const a = new Denque([1, 2, 3, 4, 5]);

    assert(a._list.length - a.length > 1);

    assert.deepEqual(a.toArray(), [1, 2, 3, 4, 5, 1]);

  it("Should add single argument - exact capacity", function () {

    const a = new Denque([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]);

    assert(a._list.length - a.length === 1);

    assert.deepEqual(a.toArray(), [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 1]);

  it("Should add single argument - over capacity", function () {

    const a = new Denque([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]);

    assert(a._list.length / a.length === 2);

    assert.deepEqual(a.toArray(), [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 1]);

describe('Denque.prototype.unshift', function () {

  it("Should unshift falsey elements (except undefined)", function () {

    assert.deepEqual(a.toArray(), [1, 1, 2, 3, 4, 5]);

    assert.deepEqual(a.toArray(), [1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]);

    assert.deepEqual(a.toArray(), [1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]);

describe('Denque.prototype.pop', function () {

  it("Should return undefined when empty denque", function () {

  it("Should return the item at the back of the denque", function () {

    const a = new Denque([1, 2, 3, 4, 5, 6, 7, 8, 9]);

describe('Deque.prototype.shift', function () {

		@@ -5,7 +5,4 @@ 'use strict';
		* Custom implementation of a double ended queue.
		* This is almost double the performance of petkaantonov's double-ended-queue lib. ¯\_(ツ)_/¯
		* 24 mil ops/s compared to 14 mil
		*
		*/
		class QueueList {
		module.exports = class Denque {
		constructor(array) {
		@@ -251,5 +248,2 @@ // circular buffer
		}

		}

		module.exports = QueueList;
		};

		{
		"name": "denque",
		"version": "1.0.2",
		"version": "1.0.3",
		"description": "The fastest javascript implementation of a double-ended queue. Maintains compatability with deque.",
		@@ -5,0 +5,0 @@ "main": "index.js",

		@@ -95,3 +95,3 @@ 'use strict';
		const a = new Denque();
		const before = a.length;
		// const before = a.length;
		let ret = a.push(0);
		@@ -159,3 +159,3 @@ assert.strictEqual(ret, 1);
		const a = new Denque();
		const before = a.length;
		// const before = a.length;
		let ret = a.unshift(0);
		@@ -162,0 +162,0 @@ assert.strictEqual(ret, 1);

Improved metrics

Worsened metrics

		# DENQUE

		[![Coverage Status](https://coveralls.io/repos/github/Salakar/denque/badge.svg?branch=master)](https://coveralls.io/github/Salakar/denque?branch=master)
		[![dependencies](https://img.shields.io/david/Salakar/denque.svg)](https://david-dm.org/Salakar/denque)
		[![build](https://travis-ci.org/Salakar/denque.svg)](https://travis-ci.org/Salakar/denque)
		@@ -9,4 +8,6 @@ [![npm version](https://img.shields.io/npm/v/denque.svg)](https://www.npmjs.com/package/denque)

		Extremely fast [double-ended queue](http://en.wikipedia.org/wiki/Double-ended_queue) implementation. Double-ended queues can also be used as a:
		Extremely fast and lightweight [double-ended queue](http://en.wikipedia.org/wiki/Double-ended_queue) implementation with zero dependencies.

		Double-ended queues can also be used as a:

		- [Stack](http://en.wikipedia.org/wiki/Stack_\(abstract_data_type\))
		@@ -19,2 +20,4 @@ - [Queue](http://en.wikipedia.org/wiki/Queue_\(data_structure\))

		Requires Node.js v4+, io.js v3+ or any platform supporting ES6 classes (pretty much all browsers).

		# Quick Start
		@@ -21,0 +24,0 @@