Have a look at a minimalist web-based file manager I made.
The source code is readily available in the angular-cloudgap repository on GitHub.
As you probably guessed, the front-end is built using AngularJs.
The back-end is ASP.NET based, but what that really means is that the HTTP services are written using Web API 2 and you could use whatever you wanted to host the files for the client application.
Hopefully it is simple enough not only to use but to go through and understand how it was made.
The application was written with a Minimum Viable Product (MVP) mentality, so it’s not fully featured but should have enough meat to be useable.
I’m drafting up an article to go through the process of building the app but it turns out I’m a slow writer, so enjoy the source code while I prep it!
I’ll try and post more details as soon as I can.