Skip to content
Permalink
Branch: master
Find file Copy path
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
80 lines (59 sloc) 1.84 KB

Async & Await / Promises

Async

Main function

(async () => {
  throw new Error('Hello World');
})().catch((err) => console.error(err));

With Promises

async () => {
  await new Promise(...);
  const [
    result1,
    result2,
  ] = await Promise.all([
    new Promise(),
    new Promise(...)],
  );
  return value;
}

Promises

When you start chaining a lot of promises and passing variables around, consider usings aysnc instead.

Pay attention to the style, because it's really stupid.

const start = new Promise((resolve, reject) => {
  xhr.get(url)
    .success((result) => resolve(result))
    .failure((error) => reject(error));
});

const afterStart = (startResult) => new Promise((resolve, reject) => {
});

start
  .then(afterStart)
  // Always start on a new line, its easier to catch
  // Always use a Promise or only { Promise.all([]) }, its eaiser to catch
  .then() => new Promise((resolve, reject) => {
  })
  .catch((error) => {
    console.log(error);
  });
  • Always have a catch() to ensure you can see all errors.

Promise.all

Gotcha:

  • You have to call .catch() on each of the promises
  • You should only catch things which are idempotent; for example:
    • Sending emails
await Promise.all([
  ...,
  ...,
].map((promise) => promise.catch(error => console.error(error))));
You can’t perform that action at this time.