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https://github.com/sindresorhus/p-progress

Create a promise that reports progress
https://github.com/sindresorhus/p-progress

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Create a promise that reports progress

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README 

        
# p-progress



> Create a promise that reports progress



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



## Install



```sh

npm install p-progress

```



## Usage



```js

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](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Promise), 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.



```js

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`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/allSettled) but also exposes the total progress of all of the promises like `PProgress.all`.



```js

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](https://github.com/sindresorhus/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](https://github.com/sindresorhus/p-cancelable) - Create a promise that can be canceled

- [More…](https://github.com/sindresorhus/promise-fun)