I'm assuming you're not working as a coder yet - obviously you should be getting your code reviewed at work if you are :)
- Have a look around for local javascript meetups, they're often a good place to start. Some literally have directories for mentors, events for juniors, etc. Depends on your location of course.
- There are some online options like codereview.stackexchange.com
- You might like the feedback you get from participating in coding challenges, eg. www.codewars.com
- If you're game, you could start doing small contributions to open source projects. Your mileage on code review will vary massively; have a look at the feedback other people are getting on a project before you commit your time to it. But if you find a project with an active community, with good (friendly but useful) feedback on PRs, it might be a way to get feedback on your coding style.