Are commas necessary in Node.js?

Question

Are there risks incurred when omitting commas in variable declarations for node.js? For example, declaring some global variables like the following works just fine:

express = require('express')
jade = require('jade')

And I don't want to write commas if it's safe not to write them (I don't care about "beauty/clarity of code" arguments).

Important: I mean commas, not semicolons (got 3 answers about semicolons). It's perfectly OK and even recommended to remove semicolons from node.js. The creator of npm also does it: http://blog.izs.me/post/3393190720/how-this-works

If in doubt, check the latest javascript specs: http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf

Note that you also don't need to write

var

for global variables.

But this question is about "commas" so please don't replace commas by semicolons by mistake when editing my question (done before).

The example you included doesn't need commas, and I can't think of a situation where a comma is optional. — JohnnyHK, Feb 20 '13 at 13:14
Can you show a better example? Nobody would put commas between global variable declaration lines; semicolons, yes, but not commas. — JohnnyHK, Feb 20 '13 at 13:24
I'm not talking about global variables only. All sorts of variables. Three big javascript github projects actually separate global variables by commas, so I assumed it's common practice: https://github.com/joyent/node, https://github.com/isaacs/npm, https://github.com/visionmedia/jade — user1943231, Feb 20 '13 at 13:33
Hmm...I still don't see what you're talking about. Can you reference a specific file in one of those projects that separate globals by commas? — JohnnyHK, Feb 20 '13 at 13:52
DO you meen the comma operator?? https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Operators/Comma_Operator — Jean-Philippe Leclerc, Feb 20 '13 at 17:22

Alex Wayne · Answer 1 · 2014-08-08T23:29:39.297

In JavaScript, if you don't write semicolons ; they will be inserted for you, invisibly. And you may not always like where they go.

You are not technically required to end every statement with a semicolon. However, most consider it a good idea.

For more info, peruse through the results of this google search. We've been arguing about this topic for a long time.

Here's an example of why this is more complex than it appears at first glance. While you are not technically required to end every statement with a semicolon, there are a few cases where you MUST, or things break. You cannot completely omit them in most codebases.

foo.def = bar
(function() {
  // some self executing closure
})()

Looks simple enough right? Well the interpreter looks at that and does this:

foo.def = bar(function() {
  // some self executing closure
})()

Which is probably not what you were expecting. The way to fix it, is with a semicolon.

foo.def = bar;
(function() {
  // some self executing closure
})()

There a lot of cases like this. You can either learn them all, and only use them in those cases, and when you inevitably forget you try to debug your code that's doing something so strange and bizarre that you tear your hair out hours... "what do you mean wtfvar is not a function?!? It's not supposed to be a function!"

Or you can just use semicolons with consistency.

Is it me or your code is not valid? You have one extra bracket at the end of each examples. — Jean-Philippe Leclerc, Feb 19 '13 at 23:11
@user1943231 You say _"Are there risks incurred when omitting commas in variable declarations for node.js?"_ Which only really makes sense with semicolons. Which is why we are all confused... You are going to have to further explain just how you _think_ you need to use commas. — Alex Wayne, Feb 20 '13 at 16:33

score 0 · Answer 2 · answered Feb 19 '13 at 22:53

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In short, no. The problems you are likely to run into will arise when you go to do things like code minifying and the compiler thinks that your two statements are one. Anyhow, if you choose not to use commas/semicolons, which is absolutely not recommended, you should be fine.

answered Feb 19 '13 at 22:53

Hacknightly

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A minifier that breaks your code? Please tell me the name so I never use it. – Jean-Philippe Leclerc Feb 19 '13 at 22:57
Guys, I'm talking about COMMAS, not semicolon – user1943231 Feb 20 '13 at 13:10

score 0 · Answer 3 · edited May 23 '17 at 12:33

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Node.js uses the V8 engine to read your code so it will pretty much behave like in Google Chrome. That said, not using semicolons is generaly a bad practice. The interpreter will try to understand your code and may be sometime mistaken (by your fault).

Check this out for a full explanation: Do you recommend using semicolons after every statement in JavaScript?

edited May 23 '17 at 12:33

Community

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answered Feb 19 '13 at 23:01

Jean-Philippe Leclerc

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Not using semicolons is not a bad practice: http://blog.izs.me/post/3393190720/how-this-works – user1943231 Feb 20 '13 at 13:08
If in doubt, just check the specs: http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf – user1943231 Feb 20 '13 at 13:08
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This is arguably a bad pratice. Javascsript is a language that should work the same way no matter the formatting. – Jean-Philippe Leclerc Feb 20 '13 at 17:18

score 0 · Answer 4 · answered Nov 15 '14 at 22:08

This very late answer just goes to clear confustion for others that might read this.

Since you're actually talking about commas, not semi-colons, I can only assume that you have a misunderstanding of what is implicitly being added by the engine.

Commas are not optional. And this code:

express = require('express')
jade = require('jade')

is being implicitly converted into this:

var express = require('express');
var jade = require('jade');

not this, which you might be expecting:

var express = require('express'),
    jade = require('jade');

Are commas necessary in Node.js?

4 Answers4