Raw Javascript files on WebGL integration

Hello everyone, I recently stumbled upon this site https://github.com/szydej/GazeCloud and I'd like to integrate their .js file into unity to be used for eye tracking. I think it's an amazing project and I'd like to add it to my game. I've tried the manuals here https://docs.unity3d.com/Manual/webgl-interactingwithbrowserscripting.html and successfully run them on my WebGL game but unfortunately I can't make the javascript from GazeCloud work. Can anyone provide some working example with raw .js files? Thanks a lot for your time. I appreciate any input or advise.