JarCastingdelay
Delay a promise a specified amount of time
If you target Node.js 15 or later, you can do await require('timers/promises').setTimeout(1000) instead.
Install
$ npm install delay
Usage
const delay = require('delay');
(async () => {
bar();
await delay(100);
// Executed 100 milliseconds later
baz();
})();
API
delay(milliseconds, options?)
Create a promise which resolves after the specified milliseconds.
delay.reject(milliseconds, options?)
Create a promise which rejects after the specified milliseconds.
delay.range(minimum, maximum, options?)
Create a promise which resolves after a random amount of milliseconds between minimum and maximum has passed.
Useful for tests and web scraping since they can have unpredictable performance. For example, if you have a test that asserts a method should not take longer than a certain amount of time, and then run it on a CI, it could take longer. So with .range(), you could give it a threshold instead.
milliseconds
mininum
maximum
Type: number
Milliseconds to delay the promise.
options
Type: object
value
Type: unknown
Optional value to resolve or reject in the returned promise.
signal
Type: AbortSignal
The returned promise will be rejected with an AbortError if the signal is aborted. AbortSignal is available in all modern browsers and there is a ponyfill for Node.js.
delayPromise.clear()
Clears the delay and settles the promise.
delay.createWithTimers({clearTimeout, setTimeout})
Creates a new delay instance using the provided functions for clearing and setting timeouts. Useful if you're about to stub timers globally, but you still want to use delay to manage your tests.
Advanced usage
Passing a value:
const delay = require('delay');
(async() => {
const result = await delay(100, {value: '🦄'});
// Executed after 100 milliseconds
console.log(result);
//=> '🦄'
})();
Using delay.reject(), which optionally accepts a value and rejects it ms later:
const delay = require('delay');
(async () => {
try {
await delay.reject(100, {value: new Error('🦄')});
console.log('This is never executed');
} catch (error) {
// 100 milliseconds later
console.log(error);
//=> [Error: 🦄]
}
})();
You can settle the delay early by calling .clear():
const delay = require('delay');
(async () => {
const delayedPromise = delay(1000, {value: 'Done'});
setTimeout(() => {
delayedPromise.clear();
}, 500);
// 500 milliseconds later
console.log(await delayedPromise);
//=> 'Done'
})();
You can abort the delay with an AbortSignal:
const delay = require('delay');
(async () => {
const abortController = new AbortController();
setTimeout(() => {
abortController.abort();
}, 500);
try {
await delay(1000, {signal: abortController.signal});
} catch (error) {
// 500 milliseconds later
console.log(error.name)
//=> 'AbortError'
}
})();
Create a new instance that is unaffected by libraries such as lolex:
const delay = require('delay');
const customDelay = delay.createWithTimers({clearTimeout, setTimeout});
(async() => {
const result = await customDelay(100, {value: '🦄'});
// Executed after 100 milliseconds
console.log(result);
//=> '🦄'
})();
Related
- delay-cli - CLI for this module
- p-cancelable - Create a promise that can be canceled
- p-min-delay - Delay a promise a minimum amount of time
- p-immediate - Returns a promise resolved in the next event loop - think
setImmediate() - p-timeout - Timeout a promise after a specified amount of time
- More…