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queue-promise
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queue-promise
is a small, dependency-free library for promise-based queues. It will execute enqueued tasks concurrently at a given speed. When a task is being resolved or rejected, an event is emitted.
$ npm install queue-promise
import Queue from "queue-promise";
const queue = new Queue({
concurrent: 1,
interval: 2000
});
queue.on("start", () => /* … */);
queue.on("stop", () => /* … */);
queue.on("end", () => /* … */);
queue.on("resolve", data => console.log(data));
queue.on("reject", error => console.error(error));
queue.enqueue(asyncTaskA); // resolved/rejected after 0ms
queue.enqueue(asyncTaskB); // resolved/rejected after 2000ms
queue.enqueue(asyncTaskC); // resolved/rejected after 4000ms
import Queue from "queue-promise";
const queue = new Queue({
concurrent: 1,
interval: 2000,
start: false,
});
queue.enqueue(asyncTaskA);
queue.enqueue(asyncTaskB);
queue.enqueue(asyncTaskC);
while (queue.shouldRun) {
// 1st iteration after 2000ms
// 2nd iteration after 4000ms
// 3rd iteration after 6000ms
const data = await queue.dequeue();
}
new Queue(options)
Create a new Queue
instance.
Option | Default | Description |
---|---|---|
concurrent | 5 | How many tasks should be executed in parallel |
interval | 500 | How often should new tasks be executed (in ms) |
start | true | Whether it should automatically execute new tasks as soon as they are added |
.enqueue(tasks)
/.add(tasks)
Adds a new task to the queue. A task should be an async function (ES2017) or return a Promise. Throws an error if the provided task
is not a valid function.
Example:
async function getRepos(user) {
return await github.getRepos(user);
}
queue.enqueue(() => {
return getRepos("userA");
});
queue.enqueue(async () => {
await getRepos("userB");
});
// …equivalent to:
queue.enqueue([() => getRepos("userA"), () => getRepos("userB")]);
.dequeue()
Executes n concurrent (based od options.concurrent
) promises from the queue. Uses global Promises. Is called automatically if options.start
is set to true
. Emits resolve
and reject
events.
Example:
queue.enqueue(() => getRepos("userA"));
queue.enqueue(() => getRepos("userB"));
// If "concurrent" is set to 1, only one promise is executed on dequeue:
const userA = await queue.dequeue();
const userB = await queue.dequeue();
// If "concurrent" is set to 2, two promises are executed concurrently:
const [userA, userB] = await queue.dequeue();
Note:
.dequeue()
function throttles (is executed at most once per every options.interval
milliseconds).
.on(event, callback)
Sets a callback
for an event
. You can set callback for those events: start
, stop
, resolve
, reject
, dequeue
, end
.
Example:
queue.on("dequeue", () => …);
queue.on("resolve", data => …);
queue.on("reject", error => …);
queue.on("start", () => …);
queue.on("stop", () => …);
queue.on("end", () => …);
Note:
dequeue
, resolve
and reject
events are emitted per task. This means that even if concurrent
is set to 2
, 2
events will be emitted.
.start()
Starts the queue – it will automatically dequeue tasks periodically. Emits start
event.
queue.enqueue(() => getRepos("userA"));
queue.enqueue(() => getRepos("userB"));
queue.enqueue(() => getRepos("userC"));
queue.enqueue(() => getRepos("userD"));
queue.start();
// No need to call `dequeue` – you can just listen for events:
queue.on("resolve", data => …);
queue.on("reject", error => …);
.stop()
Forces the queue to stop. New tasks will not be executed automatically even if options.start
was set to true
. Emits stop
event.
.clear()
Removes all tasks from the queue.
.started
Whether the queue is running.
.stopped
Whether the queue has been forced to stop by calling Queue.stop
.
.size
Size of the queue.
.isEmpty
Whether the queue is empty, i.e. there's no tasks.
.shouldRun
Checks whether the queue is not empty and not stopped.
$ npm test
We have prepared multiple commands to help you develop queue-promise
on your own. You will need a local copy of Node.js installed on your machine. Then, install project dependencies using the following command:
$ npm install
$ npm run <command>
Command | Description |
---|---|
test | Run all test:* commands described below. |
test:flow | Test Flow types. |
test:typescript | Test TypeScript types. |
test:unit | Run unit tests. |
test:lint | Run linter tests. |
defs:flow | Build Flow type definitions. |
defs:typescript | Build TypeScript type definitions. |
clean | Clean dist directory. |
build | Build package and generate type definitions. |
watch | Build package in watch mode. |
release | Bump package version and generate a CHANGELOG.md file. |
queue-promise
was created and developed by Bartosz Łaniewski. The full list of contributors can be found here. The package is MIT licensed.
We want contributing to queue-promise
to be fun, enjoyable, and educational for anyone, and everyone. Changes and improvements are more than welcome! Feel free to fork and open a pull request. We use Conventional Commits specification for commit messages. If you have found any issues, please report them here - they are being tracked on GitHub Issues.
FAQs
A simple, dependency-free library for concurrent promise-based queues. Comes with with concurrency and timeout control.
The npm package queue-promise receives a total of 6,809 weekly downloads. As such, queue-promise popularity was classified as popular.
We found that queue-promise demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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