One major benefit of trailing commas is that they play well with version control.
E.g. let's say you have the following array:
const myArray = [
1,
2,
];
Later, you like to add an additional element:
const myArray = [
1,
2,
3,
];
Then, the diff file looks as follows:
const myArray = [
1,
2,
+ 3,
];
And not:
const myArray = [
1,
- 2
+ 2,
+ 3
];
Which IMHO is much less descriptive.