Crockford on Bootstrap's semicolon omission: “insanely stupid code”

No, it just makes things worse. If people are going to follow the spec, they should follow it and reject bad input. Otherwise, you get a mess of code that tries to guess at what to do. This leads to inconsistencies, possibly security bugs.

Imagine if invalid HTML had been flat-out rejected by browsers since the beginning. Cross-browser compat would be, at least, somewhat easier due to less bad HTML surviving in the wild, since it simply would not have worked. In XML, for instance, I've never heard of the need to deal with invalidly formatted messages.

There's enough problems interpreting semantics, why do folks want to add syntax to the problem, too?

My argument is that ending every line with // is just noise, () is just noise, and ; is just noise, except for the one in 1000loc time that it isn't. And filling your code with noise not only makes your code harder to read and longer to type (if even by a little bit), but it trains you to ignore semi-colons, especially since you do not have a compiler complaining when you miss them. And when semi-colons fade into the background, it is MUCH harder to catch the one case where they are important.

If you were to write ruby, smalltalk, perl, google go, python, coffeescript or any of the other languages with asi, you find that people omit the semicolons in every situation unless for the few they need them, and never run into a problem. For some reason, that is not the case with js. Do all of those other languages "abuse" ASI? I work on a 500k loc ruby app, and I feel very confident in saying there has never been a single case of a bug from an ambiguous statement from asi (although there have been from the difference of && and 'and'), and there is only about 5 semi colons in the whole code base.

Now, js is different then those other languages in that it has a quirk where it treats whitespace and newlines the same for all types of brackets. Realistically (if you are writing for the browser), this only comes up in lines starting with an open parenthesis, since that is the one case where starting a new statement on a line with any kind of bracket makes sense. And even then, the one time you are likely to be doing that is for an immediately invoking function (function(){}()), which isn't exactly you do every few lines of code. So you have a choice on how to deal with this one, fairly uncommon case; either handle it in a special fashion when it occurs, or put a semi colon on every other line. I don't care which one you choose, all I ask is you afford me the same respect :)

My intent isn't to get into a silly language argument over this, but it seemed like you genuinely missed what I was trying to say. If you feel it would personally help you write better code, then more power to you. But I write a lot of semi-colonless code in various languages, and it has literally never caused a problem for me.

Ending every line with // is noise because it means nothing to the compiler or to the human. If I could write comments without prefixing them with //, I would (but the compiler won't let me). () and ; are not noise because they simplify the rules of the language. They make it so someone reading your code needs to remember fewer esoteric rules to understand it. That is a big win. Saving a single character of typing per line, for your fingers and your disk, is a miniscule win. I hope you're writing code that's more interesting than a typing contest (but if you aren't, maybe you care about the semicolons). The disk and the network don't care about one more semicolon per expression. They know about compression, they will deal with it. If your compiler doesn't complain when you miss them, you need a better compiler. Maybe a linter, or google's closure. Or maybe there's a market for a decent javascript compiler. I don't understand what you mean by "when semi-colons fade into the background, it is MUCH harder to catch the one case where they are important". If you use them everywhere and you miss one, it's easy to spot. If you have to examine each line with a set of rules in order to figure out if you actually needed one there, that's a more expensive task.

Ruby, python, and coffeescript were designed with significant newlines, and therefore designed around the corner cases. The only reason you'll need semicolons in those languages is to have two statements on the same line (coffeescript excepted, I'm not sure about it but my guess is that they did it right). These languages went to great lengths to reduce the cases where you need statement separators, and document this behavior widely and clearly. Perl requires semicolons, dunno where you got the idea it didn't. I don't know about smalltalk and go, I don't use them.

I probably did miss what you were trying to say.

In languages that weren't designed with significant newlines, everybody uses the statement separator at the end of a line, so it seems to me that moving them to the beginning of lines is just confusing. In any case, ASI is not significant newlines, it's a hack. I don't know what more to do than to just beat it into your head. It is not a feature you should rely on.

The important part of what I'm trying to express is that, in any language, the most important thing you need to do is to write explicit code. This means typing all the characters so that not only does the compiler (and tools) not get confused, but future human readers don't get confused either. Javascript intends for you to separate your statements with semicolons. If you start playing tricks with them, you are going to confuse people that try to understand (or, heavens, learn from) your code. You will get burned.

Consider this example (I'm a C guy):

    if (a && b || c && d | e || f && g)

How does this resolve? Does it help you if I write this?

    if ((a && b) || (c && (d | e)) || (f && g))

It sure as hell does. Now, these are semantically identical. But when you read the second one, you don't need to know that bitwise OR binds tighter than logical AND, and logical AND binds tighter than logical OR. These are details you should not need to remember when you read my code. Are parentheses just line noise here? I think not. I think they are quite meaningful. Not to the compiler, but to the human consumers of my code. It's costs the reader a lot more to read the first one than the second. The first one is mentally expensive. (In fact, modern C compilers will warn you about not having these parens here because they know that adding them is a good idea. If you turn on warnings.)

The same applies for ASI. If you rely on extra compiler tricks a human needs to remember, that's expensive. It is a lot better to have a simpler rule: just put a semicolon after every statement, and don't make anyone think about it again. Or put one before, I don't really care. Just do something consistent. Try to code to a simpler subset of the language, to make other programmers' lives easier.

I really don't mean this to be an attack against you or the javascript community. Well, I sort of do, because abusing ASI is stupid, but I actually mean this to be an educational experience. Let me help you mature as a programmer.

Nice, didn't know void can be prepended to a function definition.