I recently remembered the first web app that I built. It was part of my senior thesis in college -- I thought that adding a way to visualize the data I was working with would make the project more interactive and it would be able to reach more people.
It's far from perfect, and the version online is the second design and I also went through a big code refactor at some point.
I had also been writing code professionally as a software engineer for around a year when I wrote this (and was a computer science teaching assistant for a year before that), but it was just data science/analysis code instead of code for the web.
I learned a lot with the project, and a lot of that knowledge has carried over to work even recently!
The app is here: http://politicaldiscussion.herokuapp.com/! You can see the about page for more about it, and the source code is also linked in the footer!