Discussion on: Why to use async & await instead of the Promise class?

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Replies for: Wait, are you sure you know how to use promise? This is totally same as your second example which writing in Promise Obviously, nice and clean,...

I agree that in this case, there's no need for async/await, but whenenver you have logic that needs to happen between the async requests, it makes things so much cleaner.

E.g. I'm writing a Lambda that scrapes a website, then creates an Item to put into a DB, then makes the async db put:

module.exports.scraper = async event => {
  const response = await got(URL);
  // pick the HTML elements I want, e.g. top 10 headlines
  // create the Item I want to put into db (10 headlines plus a date, e.g.)
  return await client.put(params).promise();
}

Also agree with @leob though that understanding Promises is still super. You may well need to combine the two as well, e.g.

const getStuff = async () => {
  const thingOnePromise = axios.get('thingOneAPI');
  const thingTwoPromise = axios.get('thingTwoAPI');

  const [thingOne, thingTwo] = await Promise.all([thingOnePromise, thingTwoPromise])
  console.log(thingOne + " and " + thingTwo);
}

(similar example given by Wes Bos in his talk on async/await which I highly recommend: youtube.com/watch?v=DwQJ_NPQWWo)

t7yang • May 10 '20

I'm not a async await hater, for me they are isomorphic which can transform to each other. I even like to mix using promise and async await.

The main problem of this article is the examples to judge async await is better than promise is pretty bad one.

Manuele J Sarfatti • May 10 '20

Also, why is no one ever bothered by having to add that try/catch block... I don't understand. I hate it.

t7yang • May 10 '20

Yes, catch is much more elegant.

SinestroWhite • May 11 '20

Can you explain why there must be a try/catch block?

@Manuele J Sarfatti

Manuele J Sarfatti • May 11 '20 • Edited

In a classic promise you have:

const request = somePromise()
  .then(data => doSomethingWithData(data))
  .catch(error => doSomethingWithError(error))

If you switch to using await and you do:

const data = await somePromise()
doSomethingWithData(data)

but the promise fails (throws an exception), then you have yourself an unhandled exception, and the browser will most probably crash your app.

The equivalent of the classic promise is therefore:

try {
  const data = await somePromise()
  doSomethingWithData(data)
} catch (error) {
  doSomethingWithError(error)
}

PS: this is pseudo-code off the top of my head and most probably not working, it's just to give an idea