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Using async and await is generally considered to be a replacement for handling promises with then() and catch() methods:
| methodThatReturnsAPromise().then(result => { | |
| handleResult(result) | |
| }).catch(err => { | |
| handleAnyExceptions(err) | |
| }) |
The promise handler shown above can be replaced with the following in an async function:
| try { | |
| var result = await methodThatReturnsAPromise() | |
| handleResult(result) | |
| } catch (err) { | |
| handleAnyExceptions(err) | |
| } |
But this method doesn’t handle errors that can come through in the then() function. Also in my opinion try ... catch leans towards arrow code. Luckily await expects a promise so we can combine promise handling with async await:
| var err, result | |
| [err, result] = await methodThatReturnsAPromise().then(res => [null, res], error => [error]).catch(error => {err = error}) | |
| if(err != null) { | |
| handleAnyExceptions(err) | |
| } else if(result != null) { | |
| handleResult(result) | |
| } |
Any errors will end up in the err variable and the result will be in the result variable. This allows you to harness the power of async await to avoid callback hell, while being able to handle errors cleanly.
Tielman Janse van Vuuren
Tielman is an experienced mobile and backend developer. Quality is his motto, no matter what programming language or platform.