Hello @sridhar-mani
vtk.js provides a subset of the functionality in VTK. If you really require to view vtu/vtk files on the web, you can try VTK.wasm which brings most of the features that are not in vtk.js to the web. The only downside is you will need to write some C++.
For example, you should be able to drop your vtu/vtk files at VTK WebAssembly demos
Right now, that demo app extracts the surface and displays a polydata. If your data is 3D volumes, you can use a C++ volume mapper instead of the polydata mapper.