The JSON format is an easy and simple way to get 3D models uploaded into a WebGL application. Lighthouse3D provides a tool (source code and visual studio project available) that uses Assim to read standard 3D model files (OBJ, Collada, 3ds, among many others) and produces a JSON formatted file containing the vertex information (positions, normals and tex coords) as well as material description.
An example of a WebGL page where such content is used is available in here.