JavaScript doesn't seem to wait for return values

Question

I\'ve been struggling with this for a while now. I\'m new to Javascript, and have been under the impression that the code I\'ve been writing has been running asynchronously.

Answer 1

I...have been under the impression that the code I've been writing has been running asynchronously.

Yes, it does. Your geocode function cannot return the results of the call to the Google API, because the function returns before the Google call completes. See note below:

function geocode(geocoder) {
    //do geocoding here...

    var address = "3630 University Street, Montreal, QC, Canada";
    geocoder.geocode({ 'address': address }, function (results, status) {
        if (status == google.maps.GeocoderStatus.OK) {
           // +---------- This doesn't return anything from your
           // v           geocode function, it returns a value from the callback
           return results;
            }
         else {
            alert("Geocode was not successful for the following reason: " + status);
        }
   });
}

Instead, you must code your geocode function so that it accepts a callback which it will call when it has the results. E.g.:

// Added a callback arg ---v
function geocode(geocoder, callback) {
    //do geocoding here...

    var address = "3630 University Street, Montreal, QC, Canada";
    geocoder.geocode({ 'address': address }, function (results, status) {
        if (status == google.maps.GeocoderStatus.OK) {
           // v---------- Call the callback
           callback(results);
            }
         else {
            alert("Geocode was not successful for the following reason: " + status);
            callback(null); // <--- Call the callback with a flag value
                            // saying there was an error
        }
   });
}

Then, instead of using it like this:

var results = geocode(someArgHere);
if (results) {
    doSomething(results);
}
else {
    doSomethingElse();
}

You call it like this:

geocode(someArgHere, function() {
    if (results) {
        doSomething(results);
    }
    else {
        doSomethingElse();
    }
});

E.g., you go fully asynchronous.