Cordova/PhoneGap exit app after twice press back button with toast ( plugin required https://github.com/EddyVerbruggen/Toast-PhoneGap-Plugin )

app-exit.js

var lastTimeBackPress=0;
var timePeriodToExit=2000;

function onBackKeyDown(e){
    e.preventDefault();
    e.stopPropagation();
    if(new Date().getTime() - lastTimeBackPress < timePeriodToExit){
        navigator.app.exitApp();
    }else{
        window.plugins.toast.showWithOptions(
            {
              message: "Press again to exit.",
              duration: "short", // which is 2000 ms. "long" is 4000. Or specify the nr of ms yourself.
              position: "bottom",
              addPixelsY: -40  // added a negative value to move it up a bit (default 0)
            }
          );
        
        lastTimeBackPress=new Date().getTime();
    }
};

document.addEventListener("backbutton", onBackKeyDown, false);

Hi, I'm using google translate to send you the message. Anyway, I've reused your "app-exit.js" script. Worked perfectly. So, how can I do it when my modal materialize is open, can not quit the application? If the modal is not open, you can quit the application. And that the user exits the modal only by the option of the exit button of the modal itself?