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  • License MIT

A Promise-based API for setTimeout / clearTimeout

Package Exports

  • await-timeout

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (await-timeout) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

await-timeout

A Promise-based API for setTimeout / clearTimeout
Build Status Npm version License

Contents

Installation

npm install await-timeout --save

Usage

The example below shows usage of timeout with ES7 async / await in try...finally block. It guarantees that timeout will be cleared in case of fetch success or any error:

import Timeout from 'await-timeout';

async function foo() {
  const timeout = new Timeout();
  try {
    const fetchPromise = fetch('https://example.com');
    const timerPromise = timeout.set(1000, 'Timeout!');
    const response = await Promise.race([fetchPromise, timerPromise]);
  } catch (e) {
    console.error(e);
  } finally {
    timeout.clear();
  }
}

The same example using .then:

function foo() {
  const timeout = new Timeout();
  return Promise.race([
    fetch('https://example.com'), 
    timeout.set(1000, 'Timeout!')
  ])
  .then(result => {
    timeout.clear();
    return result;
  })
  .catch(e => {
    timeout.clear();
    console.error(e);
  });
}

API

new Timeout()

Constructs new timeout instance. It does not start timer but creates variable for timer manipulation.

const timeout = new Timeout();

Note: having separate variable is useful for clearing timeout in finally block

.set(ms, [message]) ⇒ Promise

Starts new timer like setTimeout() and returns promise. The promise will be resolved after ms milliseconds:

const timeout = new Timeout();
timeout.set(1000)
  .then(() => console.log('1000 ms passed.'));

If you need to reject after timeout:

timeout.set(1000)
  .then(() => {throw new Error('Timeout')});

Or reject with custom error:

timeout.set(1000)
  .then(() => {throw new MyTimeoutError()});

The second parameter message is just convenient way to reject with new Error(message):

timeout.set(1000, 'Timeout');
// equivalent to
timeout.set(1000).then(() => {throw new Error('Timeout')});

If you need to just wait some time - use static version of .set():

Timeout.set(1000).then(...);

.clear()

Clears existing timeout like clearTimeout().

const timeout = new Timeout();
timeout.set(1000)
  .then(() => console.log('This will never be called, because timeout is cleared on the next line'));
timeout.clear();

With ES7 async / await .clear() can be used in finally block:

async function foo() {
  const timeout = new Timeout();
  try {
    // some async stuff
  } finally {
    timeout.clear();
  }
}

Motivation

Before making this library I've researched many similar packages on Npm. But no one satisfied all my needs together:

  1. Convenient way to cancel timeout. I typically use it with Promise.race() and don't want timer to trigger if main promise is fulfilled first.
  2. API similar to setTimeout / clearTimeout. I get used to these functions and would like to have mirror syntax.
  3. Easy rejection of timeout promise. Passing error message should be enough.
  4. No monkey-patching of Promise object.
  5. Zero dependencies.

License

MIT @ Vitaliy Potapov