307 lines
8 KiB
Markdown
307 lines
8 KiB
Markdown
# fastq
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![ci][ci-url]
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[![npm version][npm-badge]][npm-url]
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Fast, in memory work queue.
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Benchmarks (1 million tasks):
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* setImmediate: 812ms
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* fastq: 854ms
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* async.queue: 1298ms
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* neoAsync.queue: 1249ms
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Obtained on node 12.16.1, on a dedicated server.
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If you need zero-overhead series function call, check out
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[fastseries](http://npm.im/fastseries). For zero-overhead parallel
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function call, check out [fastparallel](http://npm.im/fastparallel).
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[](https://github.com/feross/standard)
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* <a href="#install">Installation</a>
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* <a href="#usage">Usage</a>
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* <a href="#api">API</a>
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* <a href="#license">Licence & copyright</a>
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## Install
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`npm i fastq --save`
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## Usage (callback API)
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```js
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'use strict'
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const queue = require('fastq')(worker, 1)
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queue.push(42, function (err, result) {
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if (err) { throw err }
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console.log('the result is', result)
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})
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function worker (arg, cb) {
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cb(null, arg * 2)
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}
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```
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## Usage (promise API)
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```js
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const queue = require('fastq').promise(worker, 1)
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async function worker (arg) {
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return arg * 2
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}
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async function run () {
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const result = await queue.push(42)
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console.log('the result is', result)
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}
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run()
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```
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### Setting "this"
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```js
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'use strict'
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const that = { hello: 'world' }
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const queue = require('fastq')(that, worker, 1)
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queue.push(42, function (err, result) {
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if (err) { throw err }
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console.log(this)
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console.log('the result is', result)
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})
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function worker (arg, cb) {
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console.log(this)
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cb(null, arg * 2)
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}
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```
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### Using with TypeScript (callback API)
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```ts
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'use strict'
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import * as fastq from "fastq";
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import type { queue, done } from "fastq";
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type Task = {
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id: number
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}
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const q: queue<Task> = fastq(worker, 1)
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q.push({ id: 42})
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function worker (arg: Task, cb: done) {
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console.log(arg.id)
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cb(null)
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}
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```
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### Using with TypeScript (promise API)
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```ts
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'use strict'
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import * as fastq from "fastq";
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import type { queueAsPromised } from "fastq";
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type Task = {
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id: number
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}
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const q: queueAsPromised<Task> = fastq.promise(asyncWorker, 1)
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q.push({ id: 42}).catch((err) => console.error(err))
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async function asyncWorker (arg: Task): Promise<void> {
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// No need for a try-catch block, fastq handles errors automatically
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console.log(arg.id)
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}
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```
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## API
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* <a href="#fastqueue"><code>fastqueue()</code></a>
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* <a href="#push"><code>queue#<b>push()</b></code></a>
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* <a href="#unshift"><code>queue#<b>unshift()</b></code></a>
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* <a href="#pause"><code>queue#<b>pause()</b></code></a>
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* <a href="#resume"><code>queue#<b>resume()</b></code></a>
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* <a href="#idle"><code>queue#<b>idle()</b></code></a>
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* <a href="#length"><code>queue#<b>length()</b></code></a>
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* <a href="#getQueue"><code>queue#<b>getQueue()</b></code></a>
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* <a href="#kill"><code>queue#<b>kill()</b></code></a>
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* <a href="#killAndDrain"><code>queue#<b>killAndDrain()</b></code></a>
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* <a href="#error"><code>queue#<b>error()</b></code></a>
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* <a href="#concurrency"><code>queue#<b>concurrency</b></code></a>
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* <a href="#drain"><code>queue#<b>drain</b></code></a>
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* <a href="#empty"><code>queue#<b>empty</b></code></a>
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* <a href="#saturated"><code>queue#<b>saturated</b></code></a>
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* <a href="#promise"><code>fastqueue.promise()</code></a>
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-------------------------------------------------------
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<a name="fastqueue"></a>
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### fastqueue([that], worker, concurrency)
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Creates a new queue.
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Arguments:
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* `that`, optional context of the `worker` function.
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* `worker`, worker function, it would be called with `that` as `this`,
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if that is specified.
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* `concurrency`, number of concurrent tasks that could be executed in
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parallel.
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-------------------------------------------------------
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<a name="push"></a>
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### queue.push(task, done)
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Add a task at the end of the queue. `done(err, result)` will be called
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when the task was processed.
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-------------------------------------------------------
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<a name="unshift"></a>
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### queue.unshift(task, done)
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Add a task at the beginning of the queue. `done(err, result)` will be called
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when the task was processed.
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-------------------------------------------------------
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<a name="pause"></a>
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### queue.pause()
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Pause the processing of tasks. Currently worked tasks are not
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stopped.
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-------------------------------------------------------
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<a name="resume"></a>
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### queue.resume()
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Resume the processing of tasks.
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-------------------------------------------------------
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<a name="idle"></a>
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### queue.idle()
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Returns `false` if there are tasks being processed or waiting to be processed.
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`true` otherwise.
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-------------------------------------------------------
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<a name="length"></a>
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### queue.length()
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Returns the number of tasks waiting to be processed (in the queue).
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-------------------------------------------------------
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<a name="getQueue"></a>
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### queue.getQueue()
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Returns all the tasks be processed (in the queue). Returns empty array when there are no tasks
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-------------------------------------------------------
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<a name="kill"></a>
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### queue.kill()
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Removes all tasks waiting to be processed, and reset `drain` to an empty
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function.
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-------------------------------------------------------
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<a name="killAndDrain"></a>
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### queue.killAndDrain()
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Same than `kill` but the `drain` function will be called before reset to empty.
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-------------------------------------------------------
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<a name="error"></a>
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### queue.error(handler)
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Set a global error handler. `handler(err, task)` will be called
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each time a task is completed, `err` will be not null if the task has thrown an error.
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-------------------------------------------------------
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<a name="concurrency"></a>
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### queue.concurrency
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Property that returns the number of concurrent tasks that could be executed in
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parallel. It can be altered at runtime.
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-------------------------------------------------------
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<a name="drain"></a>
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### queue.drain
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Function that will be called when the last
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item from the queue has been processed by a worker.
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It can be altered at runtime.
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-------------------------------------------------------
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<a name="empty"></a>
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### queue.empty
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Function that will be called when the last
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item from the queue has been assigned to a worker.
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It can be altered at runtime.
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-------------------------------------------------------
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<a name="saturated"></a>
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### queue.saturated
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Function that will be called when the queue hits the concurrency
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limit.
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It can be altered at runtime.
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-------------------------------------------------------
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<a name="promise"></a>
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### fastqueue.promise([that], worker(arg), concurrency)
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Creates a new queue with `Promise` apis. It also offers all the methods
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and properties of the object returned by [`fastqueue`](#fastqueue) with the modified
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[`push`](#pushPromise) and [`unshift`](#unshiftPromise) methods.
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Node v10+ is required to use the promisified version.
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Arguments:
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* `that`, optional context of the `worker` function.
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* `worker`, worker function, it would be called with `that` as `this`,
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if that is specified. It MUST return a `Promise`.
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* `concurrency`, number of concurrent tasks that could be executed in
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parallel.
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<a name="pushPromise"></a>
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#### queue.push(task) => Promise
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Add a task at the end of the queue. The returned `Promise` will be fulfilled (rejected)
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when the task is completed successfully (unsuccessfully).
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This promise could be ignored as it will not lead to a `'unhandledRejection'`.
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<a name="unshiftPromise"></a>
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#### queue.unshift(task) => Promise
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Add a task at the beginning of the queue. The returned `Promise` will be fulfilled (rejected)
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when the task is completed successfully (unsuccessfully).
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This promise could be ignored as it will not lead to a `'unhandledRejection'`.
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<a name="drained"></a>
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#### queue.drained() => Promise
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Wait for the queue to be drained. The returned `Promise` will be resolved when all tasks in the queue have been processed by a worker.
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This promise could be ignored as it will not lead to a `'unhandledRejection'`.
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## License
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ISC
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[ci-url]: https://github.com/mcollina/fastq/workflows/ci/badge.svg
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[npm-badge]: https://badge.fury.io/js/fastq.svg
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[npm-url]: https://badge.fury.io/js/fastq
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