Async & Await / Promises

Async
Main function
(async () => {
  throw new Error('Hello World');
})().catch((err) => console.error(err));
With Promises
​https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function​
async () => {
  await new Promise(...);
  const [
    result1,
    result2,
  ] = await Promise.all([
    new Promise(),
    new Promise(...)],
  );
  return value;
}
Promises
​MDN​
​https://github.com/wbinnssmith/awesome-promises​
​http://bluebirdjs.com/docs/why-promises.html​
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))));
​
Array
Booleans
Last updated 1 year ago