I’d highly recommend you take a look at the Airbnb Style Guide. Although, it’s a little long and has some subjective rules, you can easily pick out your favorites and apply them to your code reviews.
Also, it’s nearly impossible to remember all the JS rules and best practices so while you’re coding I’d really recommend you use a linter like eslint. You can configure it to your preference, and many text editors will lint for you as you code. You can even have eslint extend the airbnb style guide which is huge to be able to follow best practices from the start until you memorize them.
Best of luck!