Brush up on DOM topics if you come from a high-level framework background like React/Angular, practice building small web apps or 'widgits' in whatever framework/language you're comfortable in, leetcode always helps a bit. You're generally free to use the language/framework of your choice for remote/phone-screen questions. However you aren't able to run/debug your code, and the editor you use handles JSX & other modern web frameworks interestingly....