How to make error go to catch statement

Question

When using the firebase node library, the real time database, a promise is returned, but what happens if an exception happens in my code in the .then() method? How could I make the code go to the .catch() method? Here is the code that I am trying to make go to the catch method.

admin.database().ref('/something/something').once('value').then(function(data: admin.database.DataSnapshot) { if(data.val() === null) { return new TypeError('invalid'); } }).catch(function(err) { console.log(err); });

Orelsanpls · Accepted Answer · 2017-08-30 14:34:18Z

2

When you hear about try and catch, the third word you need to think about is throw!

throw new TypeError('invalid')

answered Aug 30, 2017 at 14:34

Orelsanpls

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Titian Cernicova-Dragomir · Accepted Answer · 2017-08-30 14:41:29Z

1

You could simplify your error handling an make you code more readable using async-await

async function asyncFunction() { try { const data: admin.database.DataSnapshot = await admin.database().ref('/something/something').once('value'); if(data.val() === null) { throw new TypeError('invalid'); } } catch (err) { console.log(err); } }

edited Aug 30, 2017 at 14:41

answered Aug 30, 2017 at 14:35

Titian Cernicova-Dragomir

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5 Comments

Orelsanpls Over a year ago

Seeing var and async/await (es8) in the same function makes me smile. Use const/let (es6)

Titian Cernicova-Dragomir Over a year ago

@GrégoryNEUT Yes, yes you are right, changed it to const :). But for async/await you don't have to wait until es8 for async-await if you use typescript :)

Orelsanpls Over a year ago

Oh that's right didn't saw that was about typescript! Nice catch

Teddy Codes Over a year ago

Your answer helped me clarify how to use async/await. Thank you!

Titian Cernicova-Dragomir Over a year ago

Glad to help, I'm a big async await fan I want to see it used everywhere :)

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