Shaving Bytes on JavaScript Conditionals
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.
![Page Visibility API]()
One event that's always been lacking within the document is a signal for when the user is looking at a given tab, or another tab. When does the user switch off our site to look at something else? When do they come back?
![Designing for Simplicity]()
Before we get started, it's worth me spending a brief moment introducing myself to you. My name is Mark (or @integralist if Twitter happens to be your communication tool of choice) and I currently work for BBC News in London England as a principal engineer/tech...
![Fx.Rotate: Animated Element Rotation with MooTools]()
I was recently perusing the MooTools Forge and I saw a neat little plugin that allows for static element rotation: Fx.Rotate. Fx.Rotate is an extension of MooTools' native Fx class and rotates the element via CSS within each A-grade browser it...
![Create a Simple Slideshow Using MooTools, Part IV: Thumbnails and Captions]()
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
and also jshint might shout about the shorter version (depending on the settings of course).
No one writes code for JSHint :)
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.
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();
Agree with the “bad practice” comments.
Sometimes you seem to post stuff just for the sake of it, or to impress beginners.
I appreciate your honesty but impressing people isn’t something that entertains me.
What if I also need to have an else branch?
There’s only “if”, I suppose. Otherwise it’s something like:
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 :)
@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.
I’m not worried about them.
What setting will make jsHint happy?
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
Readability is important, but for those who like to hyper-optimize their code, this is a great tip.