switch/case, is default really necessary?

[csdude55]

When using switch/case, I think of "default" the same as I'd think of an "else" in an if/else statement: I only use it if it's necessary.

But while optimizing my code, I see that ES Lint throws a warning on switch/case when I don't have a default.

What do you think, should I ignore the warning? Or is there an advantage to throw in an empty default?

[phranque]

it's a warning.
if the warning is of your intention you may ignore it.
think of it as a reminder in case you forgot the default.

[csdude55]

I know that, historically, sometimes those warnings become errors :-O And other times they make things run slower than necessary. So I guess that I really just wanted to make sure that this was one I could ignore.

Either way, I think that I'm going to ignore it. The juice isn't worth the squeeze, ya know? LOL

[phranque]

The juice isn't worth the squeeze

it really depends on whether your ultimate objective is to minimize errors and warning messages, or to minimize code, or to optimize code, etc

[csdude55]

The ultimate objective is to increase pages per session, and the means to that end right now is to make the page faster for the end user. Everyone says that differences are negligible and not worth worrying about, but shaving microseconds here and there has added up!

My rule of thumb is to minimize code, which decreases the size of the page being loaded and results in a faster load time. But of course that doesn't always mean that the page is faster; eg, switch/case is faster to process than if/elseif/else, regardless of the size. So if throwing this warning adds more time to the process than adding the word "default:" would increase the load time then I'd go through and add it in.

[phranque]

in that case the ultimate objective is code optimization and your answer lies in your test results.

[csdude55]

I haven't found a good way to bench test Javascript, though. I can test server-side programming easily enough, but client-side has too many variables that I can't control. I've mostly just been trusting what the docs say.

[phranque]

oh yes, i forgot this is specifically a JS question.
you're probably balancing code bloat (download speed) against the cost of logging the warning.
i'm sure code execution is essentially equal otherwise.

[lucy24]

Then again, it can't possibly add many nanoseconds if you wind up every function with

 default:
 break;

Some day you may get a visitor whose browser (the Ghost of MSIE Past, let's say) falls into a coma if it runs through the whole switch/case and never finds an applicable case.

[csdude55]

Sorry for the late reply, for some reason I haven't been getting emails from WebmasterWorld when someone replies :-/

Technically speaking, if default is last then I wouldn't even need the break, would I?

switch (foo) {
 case 'bar':
  // do something
  break;

 case 'whatever':
  // do something else
  break;

 default:
}

That doesn't throw an error, anyway.