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.
Trailing in languages which support ending the last item with a comma as this follows the usage of the semicolon.
Leading otherwise as no language I can remember supports a leading comma on the first item: 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.