Fix eslint errors in all exercises

I have configured eslint in https://github.com/exercism/javascript/pull/479

But have not fixed errors in any exercise apart from hello-world. Instead I added all exercises to .eslintignore.

The plan is to do this:

1. Pick one exercise (You can pick many but we prefer to have separate PRs so that it is easy to review - but if there are not many changes - you can pick 2-3 at once).
2. Remove the exercise name from .eslintignore file
3. Run npm run lint - This should show errors in those exercises.
4. Fix those errors - commit and raise a PR 🎉

Note: The eslint configuration is not final. I did not have a good look at all errors, just put a sensible default in place. While fixing, if you encounter some error that you feel we should allow(ignore), feel free to comment on this issue.

[thanhcng]

I’d like to work on this pls

[tejasbubane]

@lukejpreston

Are there even any errors left?

We have disabled eslint errors using .eslintignore for all exercises and plan to fix errors in 1-2 exercises at a time. This is to make CI happy for now while using it to fix errors by removing the exercises we fix. (See PRs attached to this issue for reference).

but eslint --fix will auto fix loads

It fixes most of them but not all are fixable. You are free to use it but we would like to have each PR fix only 1-2 exercises entirely. This way it is easy to manage/review PRs.