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Custom exceptions with JS

Damian Cipolat on March 06, 2020

It is very common languages such as java and c # to create custom exceptions, to differentiate error situations from one another. In JS there is ...

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Tiep Phan • Mar 6 '20

You don't need explicit call this line

class ValidationError extends Error {
  constructor(message) {
    super(message) // this one will store the message variable to message field
    this.name = 'VALIDATION_ERROR'
    // this.message = message
  }
}

Duy K. Bui • Mar 6 '20

if (!exception)
    throw exception();

Did you mean !!exception?

danielpdev • Mar 7 '20 • Edited

Good article!
It's easy to just throw error and use catch to handle the exception, but ideally you shouldn't use throw very often as it's a huge drawback on performance.

Robert Myers • Mar 7 '20

The way I've always heard, and continue to follow, exceptions are for exceptional conditions. They shouldn't be for logic flow.

In a good many of my projects (all languages), there's plenty of throws, but almost no catches at all, except maybe at or near the top level. In the case of errors, I want things to blow up. If the db goes down, there's not much I can do. If I have a bug that results in a throw, it's noisy and I have a nice stack trace right to it, fail early and noisy.

Damian Cipolat • Mar 7 '20 • Edited

Well I'm using this way in a very massive production project and we don't lose Performance. Do you have a link that supports this or what you say or experience to tell?

danielpdev • Mar 7 '20

try-catch will impact your performance only if you actually throw exceptions.
Examples:

Performance loss when exception is thrown: jsperf.com/try-catch-performance-jls
No performance loss if no exception is thrown: jsperf.com/try-catch-performance-j...

Conclusion:
I'm not saying that you should not use try-catch at all, but like in the examples above actually throwing an exception can be easily avoided.

Damian Cipolat • Mar 7 '20

Nice, thanks for the links provides very useful information. I will be investigating about this.

Renato Ruk • Mar 7 '20

Can you explain this in more detail? I guess throwing a lot of exceptions frequently may introduce performance issues, but not sure why. Is it because of the stack tracing?

Bernard Baker • Mar 6 '20

Good article.

okyanusoz • Jul 16 '21

Thanks!

Usman Khalil • Mar 7 '20

Loved it.