When to try/catch
Errors are not something to be scared of. Every program that runs in production handles errors on a constant basis. Our job as developers is to handle the errors gracefully and in a way that aligns with our expectations. Now, I will admit, one of the big criticisms I have of JavaScript is how hard it is to know whether I should expect a function to potentially throw an error or not.
In Go and some other languages, the function signature tells us if we should expect an error:
func getMovieRecord(movieId int) (Movie, error) {
// ...
}
This lets us know if we should be prepared to handle an error when we call a function. In JavaScript... we're kinda left guessing. The only way to know for sure is to read the body of the function. This might tempt you to just wrap everything in tons of try/catch blocks, but I'd advise against that.
Here are some rules of thumb for knowing when to use try/catch:
- Do you control the input?
- If the variable in question is coming from a user, an API, or some other external source, you should probably wrap its initial handling in a
try/catchblock.
- If the variable in question is coming from a user, an API, or some other external source, you should probably wrap its initial handling in a
- Is the error recoverable?
- If the error is something you can recover from, like a network request failing, you should probably wrap it in a
try/catchblock. If not, let the program crash.
- If the error is something you can recover from, like a network request failing, you should probably wrap it in a
- Are you trying to compensate for bad code?
- If you wrote some bad code that results in more errors than there need to be, don't wrap it in a
try/catchblock. Fix the code.
- If you wrote some bad code that results in more errors than there need to be, don't wrap it in a
- Is it really an abort-worthy error?
- In a lot of (especially front-end) JavaScript code, there are so many unknowns that it doesn't make sense to lose control of a program just because a variable is
undefined. That's why the optional chaining operator (?.) and nullish coalescing operator (??) were introduced... use them as needed.
- In a lot of (especially front-end) JavaScript code, there are so many unknowns that it doesn't make sense to lose control of a program just because a variable is
Which of these is a proper use of a try/catch block?