This tool will use THREE.js to render an OptiFine config file (plus texture) in the browser. It could theoretically work with JEM files too, but no promises.
It will load the model.cfg and texture.png from the same folder and generate a THREE.js scene with orbit controls. Plans are to make the URLs that it loads from configurable, as well as how it creates the scene.
The ReCape team is planning on using this for the client as a model viewer.