4 ms·

http://blog.izs.me/post/2353458699/an-open-letter-to-javascript-leaders-regarding http://blog.izs.me/post/2353458699/an-open-letter-to-javascr... That is a pre

http://blog.izs.me/post/2353458699/an-open-letter-to-javascript-leaders-regarding http://blog.izs.me/post/2353458699/an-open-letter-to-javascr... That is a pretty good rundown of the rules. The only problem with not having semicolons is cases like this, where someone is using a bad tool to minify your code. None of the tools that currently do the best job will break on that code.

leif 15y ago
Yes, tool writers need to understand this behavior and handle it. But I still don't understand why the hell you would want to do this. These are a lot of rules to remember, and I don't think it makes sense to think about them for each statement I write. Nothing here says "here is what you gain with this technique", all I see is "it's perfectly valid so quit whining". This doesn't satisfy my curiosity. Then we have this: For example, instead of this: foo(); [1,2,3].forEach(bar); you could do this: foo() ;[1,2,3].forEach(bar) The advantage is that the prefixes are easier to notice, once you are accustomed to never seeing lines starting with ( or [ without semis. So now the argument is "don't worry, you get used to writing stupid looking code"? This is getting depressing.
- mattbriggs 15y ago
  starting a line with a semicolon means "start a new expression", if it is done where it is meaningful. By putting it at the start of the line, it is easier to associate it with the statement that makes the character important, and calls out that you are paying attention to one of the biggest gotchas in the language putting a semicolon at the end of every line is basically just noise. You get used to it, and I find semi-colon bugs end up happening much more frequently. More then that, you are essentially just typing an arbitrary character 99.99999% of the time. When you need a semi colon is essentially a corner case, so the vast majority of code is just getting appended with a character which has no meaning. Its like the javascript community decided to surround all expressions with parens, since it makes things more explicit, and there are a few cases (much more common then semi colons) where you need it in the language. Or if they decided to end all lines with //, just in case someone wanted to follow it with a comment. Those two examples make as much sense as advocating semicolons at the end of each line.
  - leif 15y ago
    No. Semicolons are statement separators. Every other language that uses them as such puts them at the end of every expression, but it's fine if you want to put a semicolon at the beginning of every expression instead, except that that will confuse people coming from other languages. What's not fine is pretending like javascript has significant whitespace and then...oops! it doesn't work here so we need to add something in this one special case. That is guaranteed confusion. If your only argument is that most of the time it's unnecessary, all you're really trying to accomplish is compression (guess what, JSMin does that!) and you may as well write APL. "You get used to it" is meaningless. You get used to banging your head against a wall too, if you do it long enough. Doesn't mean it's a good idea. It's actually worse than that though, because other people need to get used to it too, so you're wasting their time as well. Surrounding all expressions (not statements) with parens does make sense, in many languages (because there are cases where you need them, and it pays to be explicit up front). That is something good style guides often dictate (like surrounding all if/else blocks with braces, even if they're only one line). Starting a comment after every line doesn't seem like a good analogy, I have no idea where you're going with that. Let me be clear, and I've now wasted a bunch of time reading up on this so it's not just opinion: ASI is a crutch added to the language in order to minimize the effect of silly errors. It is not a language feature. Python was designed to have significant newlines, and they resolved the ambiguous cases. Javascript was designed to have semicolons between statements when written correctly. Abusing ASI is error-prone and not future-proof (against programmers, apparently language spec changes are going to maintain current behavior). If you think its abuse is a good idea, you should be quarantined from the rest of the programming community. Or write your own language and design it around this.
    - mattbriggs 15y ago
      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.

leif 15y ago

Yes, tool writers need to understand this behavior and handle it. But I still don't understand why the hell you would want to do this. These are a lot of rules to remember, and I don't think it makes sense to think about them for each statement I write. Nothing here says "here is what you gain with this technique", all I see is "it's perfectly valid so quit whining". This doesn't satisfy my curiosity. Then we have this: For example, instead of this: foo(); [1,2,3].forEach(bar); you could do this: foo() ;[1,2,3].forEach(bar) The advantage is that the prefixes are easier to notice, once you are accustomed to never seeing lines starting with ( or [ without semis. So now the argument is "don't worry, you get used to writing stupid looking code"? This is getting depressing.

mattbriggs 15y ago
starting a line with a semicolon means "start a new expression", if it is done where it is meaningful. By putting it at the start of the line, it is easier to associate it with the statement that makes the character important, and calls out that you are paying attention to one of the biggest gotchas in the language putting a semicolon at the end of every line is basically just noise. You get used to it, and I find semi-colon bugs end up happening much more frequently. More then that, you are essentially just typing an arbitrary character 99.99999% of the time. When you need a semi colon is essentially a corner case, so the vast majority of code is just getting appended with a character which has no meaning. Its like the javascript community decided to surround all expressions with parens, since it makes things more explicit, and there are a few cases (much more common then semi colons) where you need it in the language. Or if they decided to end all lines with //, just in case someone wanted to follow it with a comment. Those two examples make as much sense as advocating semicolons at the end of each line.
- leif 15y ago
  No. Semicolons are statement separators. Every other language that uses them as such puts them at the end of every expression, but it's fine if you want to put a semicolon at the beginning of every expression instead, except that that will confuse people coming from other languages. What's not fine is pretending like javascript has significant whitespace and then...oops! it doesn't work here so we need to add something in this one special case. That is guaranteed confusion. If your only argument is that most of the time it's unnecessary, all you're really trying to accomplish is compression (guess what, JSMin does that!) and you may as well write APL. "You get used to it" is meaningless. You get used to banging your head against a wall too, if you do it long enough. Doesn't mean it's a good idea. It's actually worse than that though, because other people need to get used to it too, so you're wasting their time as well. Surrounding all expressions (not statements) with parens does make sense, in many languages (because there are cases where you need them, and it pays to be explicit up front). That is something good style guides often dictate (like surrounding all if/else blocks with braces, even if they're only one line). Starting a comment after every line doesn't seem like a good analogy, I have no idea where you're going with that. Let me be clear, and I've now wasted a bunch of time reading up on this so it's not just opinion: ASI is a crutch added to the language in order to minimize the effect of silly errors. It is not a language feature. Python was designed to have significant newlines, and they resolved the ambiguous cases. Javascript was designed to have semicolons between statements when written correctly. Abusing ASI is error-prone and not future-proof (against programmers, apparently language spec changes are going to maintain current behavior). If you think its abuse is a good idea, you should be quarantined from the rest of the programming community. Or write your own language and design it around this.
  - mattbriggs 15y ago
    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.