Question

When coding a library in JavaScript, what is the most standard (friendliest?) way to handle invalid input to a function? My gut tells me that returning undefined is perfectly fine, but is it actually more helpful to throw an error instead? Or does it really not matter?

I could also see returning false, null or even -1, but I don’t think those would be as widely expected.

(If this question is too subjective, I’m happy to make it cw.)

Answer 1

Advantages of exceptions:

• If an error is a rare occurrence (not expected in normal operation), then it may be easier and faster for the calling code to catch exceptions in one higher-level place rather than test return values after every API call.

Disadvantages of exceptions:

• Catching an exception is a lot slower than testing a return value so if an error is a common occurrence, then exceptions will be a lot slower.
• If the calling code is going to check errors on every API call they make (and not catch exceptions at a higher level), exceptions are more of a pain to write around every single API call than just testing a return value.