Trailing comma for function arguments and call parameters

Alex Kocharin alex at
Sun Jul 6 00:57:27 PDT 2014

Unless you use leading comma style, trailing commas are very good to have for anything that has variable amount of items/keys/arguments. 

This is a classic example I use to show why JSON is a bad idea:

I believe the same thing applies for javascript functions. If it was a bug in javascript, I wish for more such bugs really...

04.07.2014, 20:33, "Oliver Hunt" <oliver at>:
> On Jul 3, 2014, at 3:52 PM, Dmitry Soshnikov <dmitry.soshnikov at> wrote:
>>  Hi,
>>  Will it makes sense to standardize a trailing comma for function arguments, and call parameters?
>>  We have it for Array and Object initialisers, and people like using them for long lists with prediction of new items adding in the future:
>>  ```
>>  var modes = [
>>    read,
>>    write,
>>  ];
>>  var platforms = {
>>    web,
>>    canvas,
>>  };
>>  ```
> I suspect, but brendan could tell us otherwise, that the allowance of trailing commas is a result of a bug in the _early_ _early_ days of JS, which then got matched by the wonders of bug for bug compat, and so became necessary for web compatibility.
> Also, i’m not sure that your intended uses is sufficiently compelling to justify non-backwards compatible syntax (i’m not against adding new syntax, i just feel that it needs to have substantial benefits)
> Hence, i don’t think this should be extended to other constructs.
> —Oliver
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