Go to this website and choose a file with a CAS mesh.
I've been playing around with Typescript and Three.js recently and implement some of the DBPF and TS4 formats. The experimental result is ts-sims4 library. Here are some nice things about it:
It runs in a browser!
It's a open-source project!
It is still a WIP project and I can't guarantee frequent updates due to schedule constraint. However, I did make a simple demonstration of what it can achieve. The CAS Viewer is a demo website to show the meshes inside a CASP package. It's been tested on the latest Chrome. However, nothing is perfect and here is the catch:
It can't read big files. Please don't test it on the game data files. It will crash.
It only reads the mesh linked from the first CASP entry.
It only reads the mesh inside the package you opened.
That being said, here is a screenshot of a shoe mesh from the base game.