Welcome to Software Development on Codidact!
Will you help us build our independent community of developers helping developers? We're small and trying to grow. We welcome questions about all aspects of software development, from design to code to QA and more. Got questions? Got answers? Got code you'd like someone to review? Please join us.
Comments on In javascript is there really a good reason to never check for boolean true || false such as if(var){}else{}?
Parent
In javascript is there really a good reason to never check for boolean true || false such as if(var){}else{}?
I am fairly certain this isn't a duplicate so please bear with me.
I check for boolean true||false using if() as a matter of course in my programming. I've programmed extensively in PHP, some in C# ASP.NET, a bit in Java, a long time ago in C++, & dabled in a few others. Checking for boolean true||false has always been pretty straightforward (as far as I could tell). But in JavaScript I've heard, read, and otherwise been told it's bad. That instead of:
if(var){}else{}
I should instead do:
if(typeof(var) !== 'undefined' || typeof(var) !== null || var !== ''){}else{}
Previous to the six months prior to asking this question (originally on StackOverflow) I was a dabbler in JavaScript. After getting tired of writing & re-writing the long version of the boolean test shown above I finally asked a friend who's done extensive js development for years. My friend supported what I'd read, that I should never test for boolean true or false the way I'm used to. However, after that discussion I have a stronger belief that if(var){}else{} IS actually completely fine in js as it works EXACTLY like I would intuitively expect it to (my jsfiddle testing this)
I've looked around and found various links. The following seemed to be the more relevant:
- Most relevant an article on the good blog javascriptweblog (Angus Croll)
- A kind of similar question on stackoverflow (which to my mind was obvious... checking for a boolean value vs an equality check...)
- Another question very similar to the above on stackoverflow
The thing that convinced me most that my usage is safe and will work fine is the 3rd answer to the first SO question I linked to above given by Incognito. The js spec is very clear about what will & will not evaluate to boolean true||false, and again this is exactly as I would have expected (though have to be reminded that an empty array is an object... but that is specific to JavaScript, while the rest of it is exactly as I would expect).
Can someone please provide a definitive reason to not check for boolean true or false in JavaScrpt, realizing I know the difference between a boolean check and an equality check??
Thanks in advance!
Post
if(typeof(var) !== 'undefined' || typeof(var) !== null || var !== ''){}else{}
is a wild thing to write for anything other than a variable that takes either undefined, null, or a string as possible values.
If you expect someVar to be a boolean, I don't know who would tell you that if (someVar) { ... } is incorrect.
If you expect someVar to be a boolean or null or undefined, or you expect it to be some other non-boolean type, then there's an argument for some sort of explicit coverage. People reading if (someVar) { ... } may expect someVar to be a boolean, even though JavaScript allows it to be other things. So if you want to express that someVar is a string, it's arguably better to write if (someVar !== '') { ... } then if (someVar) { ... } in order to make that expectation clear, even though they do the same thing. Similarly, if someVar may be a boolean or null, writing if (someVar === false || someVar === null) { ... } is clearer than if (!someVar) { ... }.
These are choices that will affect how some other people will read your code, and not what the machine will do. Programming is an act of communication and not just the puzzle of getting the machine to do the thing you want. Even the code you never share with others might be read by you five years later, and you'll be grateful then for the work you do now to save that you some time.
1 comment thread
0 comment threads