p-progress

Create a promise that reports progress

Useful for reporting progress to the user during long-running async operations.

Install

npm install p-progress

Usage

import pProgress from 'p-progress';

const runJob = async name => pProgress(async progress => {
	const job = new Job(name);

	job.on('data', data => {
		progress(data.length / job.totalSize);
	});

	await job.run();
});

const progressPromise = runJob('Gather rainbows');

progressPromise.onProgress(console.log);
//=> 0.09
//=> 0.23
//=> 0.59
//=> 0.75
//=> 1

await progressPromise;

API

pProgress(function)

Convenience method to make your promise-returning or async function report progress.

The function you specify will be passed the progress() function as a parameter.

instance = new PProgress(executor)

Same as the Promise constructor, but with an appended progress parameter in executor.

PProgress is a subclass of Promise.

progress(percentage)

Type: Function

Call this with progress updates. It expects a number between 0 and 1.

Multiple calls with the same number will result in only one onProgress() event.

Calling with a number lower than previously will be ignored.

Progress percentage 1 is reported for you when the promise resolves. If you set it yourself, it will simply be ignored.

instance.progress

Type: number

The current progress percentage of the promise as a number between 0 and 1.

instance.onProgress(function)

Accepts a function that gets instance.progress as an argument and is called for every progress event.

import {PProgress} from 'p-progress';

const progressPromise = new PProgress((resolve, reject, progress) => {
	const job = new Job();

	job.on('data', data => {
		progress(data.length / job.totalSize);
	});

	job.on('finish', resolve);
	job.on('error', reject);
});

progressPromise.onProgress(progress => {
	console.log(`${progress * 100}%`);
	//=> 9%
	//=> 23%
	//=> 59%
	//=> 75%
	//=> 100%
});

await progressPromise;

PProgress.all(promises, options?)

Convenience method to run multiple promises and get a total progress of all of them. It counts normal promises with progress 0 when pending and progress 1 when resolved. For PProgress type promises, it listens to their onProgress() method for more fine grained progress reporting. You can mix and match normal promises and PProgress promises.

PProgress.allSettled(promises, options?)

Like Promise.allSettled but also exposes the total progress of all of the promises like PProgress.all.

import pProgress, {PProgress} from 'p-progress';
import delay from 'delay';

const progressPromise = () => pProgress(async progress => {
	progress(0.14);
	await delay(52);
	progress(0.37);
	await delay(104);
	progress(0.41);
	await delay(26);
	progress(0.93);
	await delay(55);
	return 1;
});

const progressPromise2 = () => pProgress(async progress => {
	progress(0.14);
	await delay(52);
	progress(0.37);
	await delay(104);
	progress(0.41);
	await delay(26);
	progress(0.93);
	await delay(55);
	throw new Error('Catch me if you can!');
});

const allProgressPromise = PProgress.allSettled([
	progressPromise(),
	progressPromise2()
]);

allProgressPromise.onProgress(console.log);
//=> 0.0925
//=> 0.3425
//=> 0.5925
//=> 0.6025
//=> 0.7325
//=> 0.9825
//=> 1

console.log(await allProgressPromise);
//=> [{status: 'fulfilled', value: 1}, {status: 'rejected', reason: Error: Catch me if you can!}]

promises

Type: Promise[]

An array of promises or promise-returning functions, similar to p-all.

options

Type: object

concurrency

Type: number
Default: Infinity
Minimum: 1

The number of concurrently pending promises.

To run the promises in series, set it to 1.

When this option is set, the first argument must be an array of promise-returning functions.

Related

• p-cancelable - Create a promise that can be canceled
• More…