What is delay?
The 'delay' npm package is a simple utility that allows you to pause the execution of an asynchronous function for a specified amount of time. It is primarily used to introduce delays in promise chains or async functions, making it useful for testing, rate limiting, or creating time-based behavior in applications.
What are delay's main functionalities?
Basic Delay
This feature allows you to pause the execution of code within an async function for a specified duration (in milliseconds). In this example, the code waits for 2 seconds before printing '2 seconds later'.
const delay = require('delay');
(async () => {
console.log('Waiting...');
await delay(2000);
console.log('2 seconds later');
})();
Delay with Value
This feature enables you to resolve a promise with a specific value after a delay. Here, the promise resolves with the string 'Hello after 1.5 seconds' after waiting for 1.5 seconds.
const delay = require('delay');
(async () => {
const result = await delay(1500, {value: 'Hello after 1.5 seconds'});
console.log(result);
})();
Delay with Options
This feature supports passing an options object that can include an AbortSignal to cancel the delay. If the abort signal is triggered, the delay is cancelled, and the subsequent code may not execute.
const delay = require('delay');
(async () => {
await delay(1000, {signal: someAbortSignal});
console.log('This will not run if the abort signal is triggered');
})();
Other packages similar to delay
timeout
Similar to 'delay', 'timeout' is used to introduce a delay in asynchronous operations. However, it focuses more on setting timeouts for promises, potentially rejecting them if they take too long, which is a slight functional shift from simply delaying.
sleep-promise
This package offers functionality similar to 'delay' by resolving a promise after a specified timeout. The main difference is in the API design and naming conventions, but the core functionality of introducing delays in promise-based workflows is very similar.
p-timeout
While 'p-timeout' provides delay functionalities, it is primarily designed to add timeout capabilities to promises. It can reject a promise if it does not settle within a specified period, which is a feature not provided by 'delay'.
delay
Delay a promise a specified amount of time
Install
$ npm install --save delay
Usage
const delay = require('delay');
delay(200)
.then(() => {
});
somePromise()
.then(delay(100))
.then(result => {
});
Advanced usage
const delay = require('delay');
async () => {
bar();
await delay(100);
baz();
}();
Promise.resolve('foo')
.then(delay.reject(100))
.then(x => blah())
.catch(err => {
});
Promise.resolve('foo')
.then(delay.reject(100, 'bar'))
.then(x => blah())
.catch(err => {
});
async () => {
const delaying = delay(1000);
setTimeout(() => {
delaying.cancel();
}, 500);
try {
await delaying;
} catch (err) {
}
}();
API
delay(ms, [value])
Delay the promise and then resolve.
delay.reject(ms, [value])
Delay the promise and then reject.
ms
Type: number
Milliseconds to delay the promise.
value
Type: any
Value to pass down the promise chain. Overrides any existing value.
delay.CancelError
Exposed for instance checking.
delay#cancel()
Cancel the delay. Results in the promise being rejected with a delay.CancelError
error.
Related
- 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…
License
MIT © Sindre Sorhus