Async & Await / Promises

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Async
Main function
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(async () => {
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  throw new Error('Hello World');
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})().catch((err) => console.error(err));
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With Promises
​https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function​
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async () => {
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  await new Promise(...);
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  const [
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    result1,
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    result2,
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  ] = await Promise.all([
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    new Promise(),
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    new Promise(...)],
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  );
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  return value;
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}
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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.
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const start = new Promise((resolve, reject) => {
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  xhr.get(url)
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    .success((result) => resolve(result))
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    .failure((error) => reject(error));
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});
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​
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const afterStart = (startResult) => new Promise((resolve, reject) => {
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});
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​
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start
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  .then(afterStart)
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  // Always start on a new line, its easier to catch
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  // Always use a Promise or only { Promise.all([]) }, its eaiser to catch
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  .then() => new Promise((resolve, reject) => {
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  })
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  .catch((error) => {
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    console.log(error);
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  });
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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
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await Promise.all([
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  ...,
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  ...,
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].map((promise) => promise.catch(error => console.error(error))));
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Array
Booleans
Last modified 2yr ago
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