For games that use 3 buttons it even works, but for games that use 6 buttons, for example: Super Street Fighter, the USB controller and keyboard do not map correctly, the physical start button punches and the button_3 does pause.

This problem is not in emulator.js but in the 3DO core, because the 3DO core sends different inputs for games that use 3 buttons and for games that use 6 buttons it sends other inputs.