[policy, no patch] JavaScript coding standards for variable declarations

I brought up the subject in #1089300: Clean up drupal.js. Might want to cross-post to get some more people here.

I agree with this.

Regardless of what we decide on:

Inline comments have to be located above the remarked line, not behind/next to it on the same line.

jQuery has already figured this out for us. We use jQuery, so lets go with what they recommend, but with two-spaced whitespace of course:

var options, name, src, copy, copyIsArray, clone, // Keep all no assigned vars in single line.
  target = arguments[0] || {}, // Assignments on following lines.
  i = 1,
  length = arguments.length,
  deep = false;

The issue i'm seeing there is people not putting "," or ";" at the right place and create leaking vars like crazy. Misplacing a ";" won't crash the thing like in php, it'll just be silent. Unless we force "use strict";

It would be ideal but too error prone.

It's way too pedantic to enforce a rule for how to write/define variables. All of the options are perfectly legit.

Enforcing alphabetic sorting, separate vars on separate lines, and whatnot is way too specific. Code should always be written in a way that makes sense within the context and for the particular goal.

Coding standards should define how to write code, if you write it in a certain way. Only in very special edge-cases, in which it may technically, organizationally, structurally, or politically matters, coding standards may ask to write code in a certain way. But that's clearly not the case here.

For example, coding standards should say that, if you declare multiple variables on one line, then the line should not exceed 80 chars in total (with commonly known exceptions to the rule). They may also recommend that you start a new line of variable declarations instead of continuing indented on the next line. But they should also clarify how to write the code when continuing to the next line. They may also say that declarations that need a comment should be written as separate variable declarations, so it is clear to which declaration the comment refers to.

It's way too pedantic to enforce a rule for how to write/define variables. All of the options are perfectly legit.

At the end of the day, I agree. Let's just make the other issues about js doc move forward.

Closing might have been a bit premature, yes.

At the very least, the docs could point out the high-level coding style parameters, similar to those I gave as examples in #8.

Agree with #8 and #9 here. My real opinion is that we should probably follow JSLint, but not everyone seems to want it, so I'd prefer recommendations over strictness as #8 says.

feels silly to put var in front of everything, the first "var" is like "here be var statements till ye hit a semicolon"
but it also feels weird to put all no-assignment vars on a single line, isn't that what we have minification for? I usually place my no-assignment ones last, but all on a separate line
I would, however, prefer to set the indentation to variable name, like so:

// comment
var foo = 'foo',
    // comment
    bar = {
      // comment
      'meh' = 'bla',
      // comment
      'bla' = 'meh
    },
    // comment
    baz,
    // comment
    meh;

But this is probably not the most readable format to everyone.

See #9, this is not a useful issue.

So can we at least agree on a recommendation to put in the documentation, because right now it's all random and confusing a lot of people.

Does anyone have any objection to putting a recommendation in the doc like the following:

Variable declaration

It is not recommended not to mix assignment and no-assignment variables under a single var statement.
Additionally, it is preferred to use multiple var statements in combination with new-lines to avoid having variables accidentally leak into the global scope.

// confusing
var foo = 'bar', x, y, meh = 'bla';

// error-prone
var foo = 'bar',
    x,
    y,
    meh = 'bla';

// better
var x, y;
var foo = 'bar';
var meh = 'bla';

All good for me, maybe add a sentence about comments that should be above the variable, not after, on the same line.

I'm fine with adding that, but the docs already state

Comments should be on a separate line immediately before the code line or block they reference.

oh ok then, don't mind me :)

Added #16 to #1778828-7: [policy, no patch] Update JS coding standards

Thanks :)