Caused by: netscape.javascript.JSException: ReferenceError: Can’t find variable: lat

i have a javaFx webview map with ” open Street Map ” , i want to get the latitude and longitude from js to Java , but it shows me this error :

Caused by: netscape.javascript.JSException: ReferenceError: Can't find variable: lat

Java

       url = this.getClass().getResource("map/index.html");
        webengine.load(url.toString());

        String fullName = (String) webview.getEngine().executeScript("lat");

        System.out.println("Lat: " + fullName);

Java Script

let lat;
 let lon;
map.on('click', function (e) {
    lat=e.latlng.lat;
    
          lon =  e.latlng.lng;
          
          lati=document.getElementById('latitude').textContent = lat;
         loni=document.getElementById('longitude').textContent = lon;

});

i want to get the lat from js to java , Anyy Solution ?