Fabio Russo

Posted on May 20, 2018 • Updated on Jul 8, 2018

There's no "else if" in JS

#javascript #think #conditional

Grammar is not a joke...

Exactly, in Javascript's grammar there's no else if statement.

How many times have you used it before? Why It's still working?

We always code like this:


function wow(arg){

  if(arg === "dog"){
    return "LOVELY";
  }
  else if(arg === "cat"){
    return "CUTE";
  }
  else return "gimme an animal";
}

wow("cat");
//-> "CUTE"

But what's really happening is this:


function wow(arg){

  if(arg === "dog"){
    return "LOVELY";
  }
  else {
    if(arg === "cat"){
        return "CUTE";
    }
    else return "gimme an animal";
  }
}

wow("cat");

What's happening here?

Literally, we're using some implicit JS behavior about {} uses.

When we use the else if statement we're omitting the {} but Javascript It's still working because It does not requires the parentheses in that case, like in many other cases!

...so what?

I'm not writing this post, just because It's something really curious to know.

I'm writing this to make you think about all the good parts or right ways to code, that forces you to write code in a way, that sometimes It's not really the best way.

There's a lot to discuss about implicit and explicit declaration of stuff like: coercion, parentheses, semicolon...

But the true always stands in the middle!.

If you just follow some specific rules on how to... you're not understanding why those rules were written, and this else if should make you think about It.

How many time have you written code, because someone told you to do so but you were totally blind about It?

I bet, a lot.

I'm not saying that we should not care about ALL those rules, and that we should know ALL the JS documentation.

I'm just saying that right now, your duty is to write good code that can be understood by someone else and to go that way... some rules are ok, but you should know the why.

Because someone is good at code, It does not mean that you have to follow his golden rules.

What's implicit for him, maybe explicit for you and many other people.

If you don't have the same knowledge, about that specific argument (and It's not possible to have exactly the same level of know about It in every single part of the code) you've two options:

Do what he's telling you to do... If It works.
Go out and check the why

Always care about the good parts but first of all, always care about your knowledge and don't code just by rules.

Best-practices must be accepted by many people

think

Latest comments (98)

Jodi Winters • Feb 12 '20

I'm not a compiler guru or have scoured the V8 code, but for languages that support this, the relevant BNF typically goes something like:
if-stmt ::= if <condition> <stmt> [else <stmt>] [;] stmt ::= <expr> || <expr-block>
I.e. it's not an implicit set of brackets, it's one statement or a statement block.
If you're wondering why we do these things as rote, it's largely fashion. This is the fashionable way to write code at the moment. Many codebases are time capsules for the standards of the time, which is why everyone wants to rewrite them every 5 years! In only the last month or so, suddenly arg => arg is out of fashion (now has to be (arg) => arg)! In fact, seniors would most likely say your example should be a switch, but that's literally a dirty word these days (I had go way down the comments to find someone suggest it!), even though it's meant for exactly that situation. The fact you did this example in a small function and did returns is a relatively new phenomena.
The reasons for being overly syntactical were quite sane at the time. For example, the reason why we used to explicitly put brackets round every block in an if statement was because:

it was less prone to people forgetting that you needed them when you wanted multiple statements in the true/false statement
It was a less sophisticated development environment that could hardly do syntax highlighting let alone auto-linting and auto-indenting
Developers very much had coding styles, you didn't need to check the git log, not that git was around at the time
It was linted by humans and the consistency improved scanning speed
Where you threw debug statements into those condition blocks so regularly it helped if they were already there
It improved code reviews because your diff didn't alter lines above and below your commit with adding brackets when it became a statement block (surprised that one's not still valid, airbnb :D )
It was when you faced functions that were several hundred lines of code, and most if/else statements had many statements in them!

I don't think it's necessary for everyone to know these sorts of reasons why they're spared the extra syntax. But without going through the pain, we wouldn't know what were the good bits. But.. just maybe... you might have some more sympathy for the senior devs out there! :D

Mihail Malo • Feb 13 '19 • Edited

The brackets, if you put them in, do a great job of showing why the conditions up to a success are evaluated, but the ones after aren't.

No, I don't mean leaving brackets in your code is okay, I meant it as an exercise.

kenorb • Nov 14 '18

Please re-read: w3schools.com/js/js_if_else.asp

Use else if to specify a new condition to test, if the first condition is false.

Will F • Oct 6 '18

I don't understand how this could be true :/

josef256 • Jul 26 '18

"dont do this.. dont do that.."
THE"if" you gonna need it.. wether your boss,your mentor, your mom tell you not to do so.

Guney Ozsan • Jul 26 '18

I don't think one can design a computer without any logic gate. And, transformation doesn't change how a thing is designed.

Nihar Raote • Jul 10 '18

I'm intrigued by what you said about if-statements. I'm curious to know how you would write the following callback function.

someRequest(URL, (err, result) => {
    if (err) {
        console.log(err);
    } else console.log(result);
}

I'm still a novice so it's difficult for me to imagine doing some things without if-statements. I would appreciate it if you could show me😅🙂.

K • Jul 10 '18

You could use something like promises.

someRequest(URL)
.then(result => console.log(result))
.catch(err => console.log(err));

Nihar Raote • Jul 12 '18

Ooh. That's right. Forgot promises could do that😅. Thanks 😊

plainJavaScript • Jul 6 '18 • Edited

function wow(arg)
{
if (arg === "dog") return "LOVELY";
if (arg === "cat") return "CUTE";
return ("gimme an animal");
}

wow("cat");
//-> "CUTE"
// or

function anotherWow()
{
return (arg === “dog”) ? “LOVELY”:((arg === “cat”) ? “CUTE”:”gimme an animal”);
}
anotherWow(“cat”);

Fabio Russo • Jul 8 '18

Yah... but what? 😅

Josh Cheek • Jul 6 '18 • Edited

Here are two real-world pieces of code I wrote yesterday. I describe the problem I'm solving, link to the relevant resources that led me to write that code, and include the if statement laden code I wrote. Your absolutism and your certainty has me rolling my eyes, so go ahead and prove me wrong! Rewrite my code without if statements in a way that's better: gist.github.com/JoshCheek/71623a73...

Phoebe Goldman • Jun 17 '18

I mean, else if is syntactic sugar for else { if ... } as opposed to being a special language construct (like Python's elif), but it does exactly the same thing. You could write basically the same article about how C pointers are just integers, or about how a switch statement is just syntactic sugar for something nasty-looking with goto, or any number of things. A more honest post might talk about how a CPU can't execute JavaScript, so it gets translated into machine code - else if and else { if look the same at that level, since they mean the same thing. Which one is syntactic sugar for the other doesn't really matter, and, as others have mentioned in this thread, I'd argue that actually the else { if version adds an additional language construct (which is why if (true) alert('alert!') works) and is therefore the more honest version.

DevelCharlie • May 31 '18

99% of businesses ????????
If you consider that COBOL has been back ...
If you consider that many banks prefer continue with old COBOL (not the new one) for the ATM services.
I you consider that big manifactures build products IoT with a poorly code and very buggy.
I think that you're developing for excelence, despite I've seen in your code of elixir-iteraptor some IF statement

DevelCharlie • May 30 '18

And the folk thinks that PHP syntax is rubbish? When in JS you can use ; or not at all? Or many coders sometimes use var or not at all. Ignoring the importance of var ... If you speak of JS you cannot say "Grammar is not a joke"

Fabio Russo • Jun 1 '18

Nope... I don't agree.
If you know grammar, you know where to use ";" and where to use "var".
If you dunno It, you just code by memory.

Paul Smith • May 30 '18

"there is a golden rule"... Sometimes I sacrifice efficiency for readability, sometimes I do the opposite. To say one size fits all is arrogant, narrow minded and not teaching good practices. There should be a good reason to do everything we do, even if it is not the most appropriate it can still be the correct choice for that instance