Deno: [deno fmt]: Trailing comma

[timreichen]

When calling deno fmt and a list of properties/values are long, it will append an unnecessary comma after the last one.

const object: { longName: boolean, otherLongName: boolean } = { longName: true, otherLongName: false }

```sh
deno fmt

Output:
```ts
const object: { longName: boolean; otherLongName: boolean } = {
  longName: true,
  otherLongName: false,
};

That can result in pretty weird looking code when it is more complex. Is this intentional?

[jeroenptrs]

Far from unnecessary. Starting from ES5, trailing commas are gradually being accepted and preferred since this reduces confusion.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Trailing_commas

It's also the standard option when using prettier (and obviously dprint defaults to this as well, as you can tell).

_edit:_ regarding the confusion bit, the MDN docs explain it perfectly:

If you want to add a new property, you can simply add a new line without modifying the previously last line if that line already uses a trailing comma. This makes version-control diffs cleaner and editing code might be less troublesome.

[timreichen]

Thank you for the link and the explanation. In that case it is therefore intentional.