Is a simple `continue` statement an acceptable alternative to nesting an entire for..in loop's body in the `if`?

Question

Typically, the solution to for..in's notorious caveat is something along the lines of:

for(var prop in obj) {
    if(obj.hasOwnProperty(prop)) {
        foo(); bar(); baz();
    }
}

I feel like it would be cleaner to just do:

for(var prop in obj) {
    if(!obj.hasOwnProperty(prop)) continue;
}

The question is... Are they not functionally identical?

they are identical as much as the code logic is concerned (they may be different by performance or something else). I prefer the second version because you get rid of a layer of indentation — Gabi Purcaru, Nov 19 '12 at 15:13
It is a matter of style and preference. The first _positive_ example makes more sense to me. _If this, then do that._ seems more meaningful than the negative _If not this, do nothing_ — Michael Berkowski, Nov 19 '12 at 15:13
See - two comments come in within seconds of each other, having opposite viewpoints. Entirely up to preference. — Michael Berkowski, Nov 19 '12 at 15:14
http://stackoverflow.com/questions/6071762/unexpected-continue — Oleg, Nov 19 '12 at 15:14
I have a third option: extract a function from `if` body and name it nicely — Tomasz Nurkiewicz, Nov 19 '12 at 15:14
@GabiPurcaru If you'd have made an answer of that, I'd have **accepted** it. — wwaawaw, Nov 19 '12 at 15:16
@MichaelBerkowski you can also think of it as _"unless this, move on to the next item."_ — wwaawaw, Nov 19 '12 at 15:17
@adlwalrus no I didn't - it really is a matter of style; I perhaps should have mentioned that they do the same thing, but I figured you'd probably determined that empirically. — Pointy, Nov 19 '12 at 15:18
@Pointy: It is a matter of style as to which you use, because they are functionally equivalent, but the OP wants confirmation that they are functionally equivalent which is not a matter of style at all. — Lightness Races in Orbit, Nov 19 '12 at 15:18
@adlwalrus I said _may_ be different performance-wise. I won't post an answer when I'm not sure I'm right — Gabi Purcaru, Nov 19 '12 at 15:19
@LightnessRacesinOrbit: Ha, wish I could +1 your question-edit comment — Travesty3, Nov 19 '12 at 15:22

score 4 · Accepted Answer · answered Nov 19 '12 at 15:17

4

They are functionally identical. Period.

As for the matter of style, Douglas and his JSLint say: don't use continue:

Avoid use of the continue statement. It tends to obscure the control flow of the function.

See http://javascript.crockford.com/code.html and search for "continue"

answered Nov 19 '12 at 15:17

Oleg

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Jesus christ, I hate crockford and his fearmongering. – wwaawaw Nov 19 '12 at 15:22
1

Indeed. It obscures the control flow of the function only for those incapable of basic reading. Which, admittedly, covers a big chunk of the JS userbase... – Lightness Races in Orbit Nov 19 '12 at 15:31
1

@adlwalrus: Crockford also seems to contradict Douglas on var declarations and spacing before the brackets in function declarations `function foo() {...}` versus `function bar () {...}`, to name a few. I think it really comes down to personal preference in these cases. (http://javascript.crockford.com/code.html#variable%20declarations) – Cerbrus Nov 20 '12 at 07:46
1

@Cerbrus There's no contradiction. Spacing before brackets, according to JSLint, is encouraged when the function literal is anonymous, such as `function () {}`. The reasoning behind this is quite solid and deserves a quote: "If the space is omitted, then it can appear that the *function's name is* **function**, which is an incorrect reading." I would also like to note, that this discussion went a bit outside of the scope of the question. Let's stop it at this point. Thanks. – Oleg Nov 20 '12 at 08:31

score 1 · Answer 2 · answered Nov 19 '12 at 15:16

Yes, they are functionally identical.

I'd say the continue-less example is a little more semantic, though.

In the first example, you aren't negating the bool in your if, so, you have a typical
if(property){"Execute the rest of this loop"}
instead of
if(not property){"Do not execute the rest of this loop"}

Is a simple `continue` statement an acceptable alternative to nesting an entire for..in loop's body in the `if`?

2 Answers2