Ask HN: Do you prefer tailing or leading comma?

1 pointsaabbcc12411y ago4 comments

In the js space, people often leave a tailing comma at the end of each line, when writing the elements of an array.

I was the practise of using leading comma in Elm, where we put a comma at the beginning of each line, when writing elements of a list.

I'm also using leading comma (and leading and/or) when writing sql query.

For example:

    select
      user.id
    , user.username
    from user
    where user.ban_time is null
      and user.activate_time is not null

4 comments

Trailing in languages which support ending the last item with a comma as this follows the usage of the semicolon.

  [ 1, 
    2, 
  ]

Leading otherwise as no language I can remember supports a leading comma on the first item:

  [ 1 
  , 2 
  ]

The entire point of this is to avoid needing to edit the prior line when inserting items into an existing lexical list this makes the diffs just:

instead of:

  - 
  +
  +

If you don't care about how your line diffs look, don't bother. Just auto-format your code instead.

dsq1y ago

For me leading commas make stuff easier to debug, you don't have to worry about the commas when you comment out the line on the select statement.

Leading comma seems more intuitive because it immediately signals the end of an entry next to the entry.

I just hit format code and let the IDE or formatter worry about it.

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