Beware that we don’t have a 1 to 1 capability mapping between VTK/C++ and VTK/js but with the itk.js infrastructure we have some path to convert C++ code to web assembly. (We’ve mostly used it for the readers)
Now that’s said, we have a pretty neat OpenSource application (ParaView Glance) leveraging itk.js + vtk.js which provides some good features for medical datasets that is fully client based. This can be a good project for reference.
Also, depending of the amount of data and processing that you want to handle, you might need a server with ITK and/or VTK. And a ParaViewWeb type of infrastructure could be meaningful.
In general, if you need help, Kitware can provide support and/or development. On top of maintaining those OpenSource frameworks, we are helping customers to build or migrate their application using our Web solutions.