Is it possible to catch exceptions thrown in a JavaScript async callback?

Question

Is there a way to catch exceptions in JavaScript callbacks? Is it even possible?

Uncaught Error: Invalid value for property 

Answer 1

You can indeed catch exceptions that fire within a JavaScript callback function.

The key is to set up the try/catch block within the callback code, as any try/catch blocks outside the callback code will have already exited by the time the callback code is executed. So while your try/catch block above won't be able to catch any exceptions that get thrown when the callback function is called, you can still do something like this:

// this will cause an exception ing google.maps.Geocoder().geocode() 
// since it expects a string.
var zipcode = 30045; 
var map = new google.maps.Map(document.getElementById('map_canvas'), {
    zoom: 5,
    center: new google.maps.LatLng(35.137879, -82.836914),
    mapTypeId: google.maps.MapTypeId.ROADMAP
});
// exception in callback:
var geo = new google.maps.Geocoder().geocode({ 'address': zipcode }, 
   function(geoResult, geoStatus) {
      try {
          if (geoStatus != google.maps.GeocoderStatus.OK) console.log(geoStatus);
      } catch(e){
          alert("Callback Exception caught!");
      }
   }
);

and you'll be able to capture the exception when it is thrown. I wasn't 100% sure whether that would be the case or not, so I wrote some test code to verify. The exception is captured as expected on Chrome 19.0.1055.1 dev.