I would still use else if. It makes clearer for the reader what is going on on a glance. That said it doesn't matter for how the code runs with return.

Is it preferred to chain a bunch of 'ifs' rather than the typical 'else ifs'? Or is it just whatever you want to do it fine?

Sadly JavaScript doesn't use integers, so this solution will fail if you give it a value of 0.12.

Test cases was fixed a year ago.

If you pass 0.5 to the function, it won't return the negative value;