fresh start with MDBT42Q , some specs before start toe code

https://www.espruino.com/BLE+Security

for me it was enough to have this code to disconnect unknown devices and learn new ones when holding button as per "Disconnect when an unknown address is found (whitelisting)" chapter in that guide

NRF.whitelist=[];
NRF.on('connect',function(addr) {
  if (!NRF.whitelist.includes(addr)){
    if (BTN1.read()){ // add to whitelist when button is held while connecting
      NRF.whitelist.push(addr);
      //vibrate(1,1,100,0);
    } else
        NRF.disconnect();
  }
});