Screen Recorder + audio -- 2

I need to create a code script that records the browser of the user and the audio reproduced by the computer. It would be useful to have an interface floating at the bottom right of the screen with only 2 buttons: record and stop. If that adds budget, then a simple .html page would be ok. Once "stop" is clicked, the video recording must be saved in the same folder of the script. Need the final video saved in .mp4 If you run multiple times that script, it must generate videos with different names. If you can find a way to do it in Javascript, that's much appreciated!