async_error_node

Review of Error Handling in Node motivated by this article.

Specifically:

"In summary, if you’re handling async error handling, you should really use the promises catch handler, which will allow you to effectively handle the async errors. But if you’re dealing with synchronous code, the try/catch will do just fine."

I think that's not the most accurate, best, precise, or most comprehensive suggestion.

Consider:

1. Error Handling within an Asynchronous Function, Timeout, Interval, Spawn or Forked Exec. (Will likely be Synchronous internal to the Asynchronous Function and will therefore use a try-catch block.)

2. I typically combine a try-catch block with a process.on('uncaughtException', ...) event listener:

   try {
        process.on('uncaughtException', exception => { console.error(`Exception encountered: ${exception}`) })
   
        //...
   } catch (ex) {
        //...
   } 

   This acts as a defacto catch block for any Error that bubbles up to the top-level process itself. Even Asynchronous ones.

3. Using a try-catch block with async-await notation is (probably most-)often encountered.

Topics

Remember:

//Same syntactic and semantic functionality
Error()
new Error()

Remember that the following is invalid:

T()
    .then(success => { console.log(success) }, failure => { console.log(failure) })
    .catch(ex => console.error(`Line 16 - asynch catch(): ${ex.message}`))

The .catch() chained method will handle failure.

Use

npm i && node main.js

Line 40 - Exception encountered: Error!
Line 16 - Exception encountered: Third Async Error!
Line 21 - asynch catch(): Third Async Error!
Line 25 - asynch catch(): Fourth Async Error - By Rejection
Line 47 - Exception encountered: Async Error!
Line 35 - UncaughtException encountered: Error: Second Async Error!

Observe that lines 54 and 28 are never logged:

• Line 28 is ignored since the prior .catch() methods handle Exceptions, Errors, and Rejections.
• Line 54 is ignored by setTimeout() although the try-catch block internal to the Timeout is used.

Resources and Links

1. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_promises
2. https://stackify.com/node-js-error-handling/#h-the-perils-of-async-try-catch