It's a lot of fun because it allows me to learn a lot of systems in general and pushes me to find elegant solutions which must be solid and cannot break compatibility amongst the dozens of sites and properties that the code is executed on.
My Expense Journal is a Web Application that I created with React, Redux and Firebase and hosted on Heroku. It came from my frustration with other ways of tracking my expenses. I wanted something simple that I could use on my Desktop and on my Phone.
Another reason why I built this was because I wanted to build and maintain a "real world" Web Application with technologies that I wanted to be fully comfortable with. Although I was comfortable with React, Redux, CSS3, etc. when I built this application, I wanted to gain further insight and skill with Security, Hosting, Administration and Support of a Web Application with real world customers.