Immediately starting queue of asynchronous or synchronous tasks, processing n function(s) concurrently. Dependency free.
npm install esm-async-queueQueue to create an immediately starting queue of asynchronous or synchronous functions, processing n tasks concurrently. Dependency free. Exported as an esm module. Typescript definitions included.bash
npm install esm-async-queue
`Basic usage:
Example of
javascript
import { Queue } from './index.js';const delayedResolution = (ms: any) =>
new Promise((resolve) => setTimeout(resolve, ms));
const queue = new Queue({ concurrency: 2 });
const startTime = (new Date()).valueOf();
const getElapsedTime = (since) =>
${((new Date()).valueOf() - since)}ms;queue.push(() => delayedResolution(200).then(() => console.log('a', getElapsedTime(startTime))));
queue.push(() => delayedResolution(400).then(() => console.log('b', getElapsedTime(startTime))));
queue.push(() => delayedResolution(200).then(() => console.log('c', getElapsedTime(startTime))));
queue.push(() => delayedResolution(400).then(() => console.log('d', getElapsedTime(startTime))));
queue.subscribe('idle', () => console.log('idle', getElapsedTime(startTime)));
// output:
// a 205ms
// b 406ms
// c 407ms
// d 811ms
// queueIdle 811ms
`Methods
#### constructor(opts)
Creates a new queue instance.
opts.concurrency: integer, default: 1 The limit of tasks to be processed in parallel.
#### push(function returning PromiseLike, async function, function)
Add a task to the queue. Processes immediately if the total length of existing tasks is less than the concurrency value.
Properties
length: integer count ALL tasks in the queue, including pending tasks.
tasksPending: integer count tasks that are in the queue, awaiting processing.
tasksProcessing:: integer count tasks that are currently processing.
concurrency: integer show count of maximum concurrent tasks.
Events
javascript
// Example: This script will print true when all items have been processed (after 200ms). Finally, unsubscribe.
const queue = new Queue({ concurrency: 2 });
const unsubscribe = queue.on('idle', () => console.log(queue.length === 0)); // the returning function allows you to remove a subscription
queue.push(() => delayedResolution(200));
``idle: Fired when the total queue length, including tasks processing drops to 0.
taskProcessing: Fired when a task begins processing.
taskProcessed: Fired when a task completes.
taskPushed: Fired when a task is pushed to the queue.