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Shaving Bytes on JavaScript Conditionals

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Whenever you work with JavaScript code, it's as though there's always a shorter way to code something.  You thought that a code set was basic until you found out that something was basic...er.  One of those code shortcuts can be found with conditions, specifically short if clauses.

A typical short if clause would look something like this:

if(callback) {
	callback();
}

Oddly enough this conditional can be made shorter:

callback && callback();

The && is less code than the if(){}; of course only by a few characters but does the same job. You could argue that readability suffers but that's up to individual developers.

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Discussion

  1. Daniel Imms

    It’s worth noting that JS minifiers like Google’s Closure Compiler will do this for you, so the first option is probably better so you get the readability without sacrificing performance. The Closure Compiler outputs it as this:

    callback&&callback();

    http://closure-compiler.appspot.com/home

  2. Herbut

    and also jshint might shout about the shorter version (depending on the settings of course).

  3. Richard Ayotte

    It’s bad practice though because the code is hard to maintain, debug and extend. I could write a whole blog on why doing this is bad. I see zero benefits.

  4. Maksim Chemerisuk

    Agree with comments above. I recently realized that there is no benefits of having expressions in my code so changed jshint settings and now it disallows to use them.

    IMO the expression below is pretty readable and it also takes one line:
    if (callback) callback();

  5. gotofritz

    Agree with the “bad practice” comments.

    Sometimes you seem to post stuff just for the sake of it, or to impress beginners.

    • David Walsh

      I appreciate your honesty but impressing people isn’t something that entertains me.

  6. Ana

    What if I also need to have an else branch?

    • David Walsh

      There’s only “if”, I suppose. Otherwise it’s something like:

      callback ? callback() : otherThing();
  7. Dan

    While I agree with people’s comments on code readability, I still appreciate posts like this.
    I’ve come across the ‘callback && callback();’ syntax before and had to look up wtf was going on. Had I read this post earlier, I would’ve known :)

  8. Sean

    @Dan i agree with you, posts like this are handy so you understand when you come across it in a project. Sadly, this is clearly lost on a couple of the previous commenters who already know everything there is to know.

  9. Eliazer

    What setting will make jsHint happy?

  10. Joe

    Code is better than anything, 2 JsPerf :
    – http://jsperf.com/if-statement-verses-and-operator
    – http://jsperf.com/ternary-vs-and-or-vs-if-else

  11. Phil LaNasa

    Readability is important, but for those who like to hyper-optimize their code, this is a great tip.

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