Trailing comma, or no trailing comma

Oct 6, 2017

Javascript

Git

Code Review

Linting is an essential part of development. It helps you keep a consistent level of quality and rules to stick to.

However there’s one rule that until recently I turned off. Comma-dangle.

Comma-dangle states whether the last item in a object should have a trailing comma. I used to think this was pretty useless and liked how it was without the comma. But a work mate recently brought up a good point.

Git diffs…

Say you have an object without a trailing comma on the last item…

1const object = {
2  first: "hello",                             
3  last: "goodbye"                             
4};

If I then go and add a new item to the end of that object, my git diff will look like so:

1const object = {
2  first: "hello",
3  last: "goodbye"
4  last: "goodbye",
5  final: "the end" 
6};

Notice how it says that last has changed? Because we’ve added a comma on the end… a bit annoying. If we used trailing commas:

1const object = {
2  first: "hello",
3  last: "goodbye",
4  final: "the end",
5};

Git Diff will now not complain about last as we haven’t needed to update that line, we just added final onto the end.

This seems like a small win, but when you have to review tens/hundreds of lines of code, every little thing you don’t have to double check is definitely a win!

Javascript

Git

Code Review

Trailing comma, or no trailing comma

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