Ask HN: Evaluating candidates' tech skills your firm lacks

The title mostly says it all. My company is looking for a front-end JS/react developer. We're a firm whose development staff is entirely back-end and so there's literally not a single person who can truly look at JS code and evaluate it's "goodness" to any degree other than how it looks and whether it does the job. We can't rate it for best practices, how idiomatic it is, etc.

We'd have liked to work out a small contracting agreement as part of the interview process where we give them some piece of work to do and compensate them at some reasonable market rate, but most people's current employers prohibit such arrangements.

There are also online tests like Codility, but I've found those to be of very limited utility.

This may come up somewhat frequently, but my google-fu is failing me here.