leonsilicon / p-wait-for

Wait for a condition to be true

p-wait-for

Wait for a condition to be true

Can be useful for polling.

Install

npm install p-wait-for

Usage

import pWaitFor from 'p-wait-for';
import {pathExists} from 'path-exists';

await pWaitFor(() => pathExists('unicorn.png'));
console.log('Yay! The file now exists.');

API

pWaitFor(condition, options?)

Returns a Promise that resolves when condition returns true. Rejects if condition throws or returns a Promise that rejects.

condition

Type: Function

Expected to return Promise<boolean> | boolean.

options

Type: object

interval

Type: number
Default: 20

Number of milliseconds to wait after condition resolves to false before calling it again.

timeout

Type: number
Default: Infinity

Number of milliseconds to wait before automatically rejecting with a TimeoutError.

before

Type: boolean
Default: true

Whether to run the check immediately rather than starting by waiting interval milliseconds.

Useful for when the check, if run immediately, would likely return false. In this scenario, set before to false.

resolveWith(value)

Resolve the main promise with a custom value.

import pWaitFor from 'p-wait-for';
import pathExists from 'path-exists';

const path = await pWaitFor(async () => {
	const path = getPath();
	return await pathExists(path) && pWaitFor.resolveWith(path);
});

console.log(path);

TimeoutError

Exposed for instance checking.

Related

• p-whilst - Calls a function repeatedly while a condition returns true and then resolves the promise
• More…