Creating .vtk from .bin file

Hi! I am new with .vtk and I am little bit meshed. I am using js, just need to convert my file to .vtk in order to add in my viewer based on THREE.js.
So, my question: I have some binary file, which I can parse to ArrayBuffer. How after that can I create .vtk with polydata (ASCII)? What should I use? Thanks!

Are you asking for the file format?