JSTree

1. Why VanillaJS? Because widgets should not include dependencies + it is fast + lightweight + also refreshed my knowledge of basics.
2. UI testing is hard and requires fiddling. So I skipped it for such a small task.
3. Tested only basic node logic, serialization and deserialization.
4. Work log: 10-11 hours.
5. If you want to style widget, there is custom css with million of hooks.
6. I know that commit messages are horrible, I was in flow all the time.
7. Tip: JSON does not serialize objects with circular reference and localstorage does not save js objects -> this task took most of the time.