- Review: Debugging with DevTools
- Read: Understanding bugs & errors in JavaScript
- Bookmark for future reference: Fixing JavaScript Errors
Often times, you'll be jumping into a pre-existing codebase and working with other people's code rather than writing a fresh app from scratch on your own. Sometimes the code is poorly tested or documented, and the previous developers may have moved on and taken their domain knowledge with them.
Navigating other's code, especially when it's broken, can lead you down some frustrating rabbit holes. Having solid debugging skills and understanding error messages will make this part of your job much easier.