An elaboration on an answer for SO question #14300700. (http://stackoverflow.com/questions/14300700/empty-variables-when-calling-javascript-function/14300733)

genericYiiLocation.js

function genericYiiLocation(callback) {

    console.log('genericYiiLocation: Creating location handler');

    this.longitude=  '';
    this.latitude=   '';
    this.accuracy=   '';

    var me = this;

    if (Modernizr.geolocation) {
        console.log('genericYiiLocation: Location supported');
        if (navigator.geolocation) {
            navigator.geolocation.getCurrentPosition(locateSuccess, locateFail);
        } else {
            alert('genericYiiLocation: Geolocation is not supported in your current browser.');
            callback(false);
        }
    } else {
        alert ('genericYiiLocation: no native location support');
        callback(false);
    }


    function locateSuccess(loc){
        console.log('genericYiiLocation: storing location data');
        me.longitude = loc.coords.longitude;
        callback(true, me);
    }

    // Unsuccessful geolocation
    function locateFail(geoPositionError) {
        switch (geoPositionError.code) {
            case 0: // UNKNOWN_ERROR
                alert('An unknown error occurred, sorry');
                break;
            case 1: // PERMISSION_DENIED
                alert('Permission to use Geolocation was denied');
                break;
            case 2: // POSITION_UNAVAILABLE
                alert('Couldn\'t find you...');
                break;
            case 3: // TIMEOUT
                alert('The Geolocation request took too long and timed out');
                break;
            default:
        }
        callback(false, geoPositionError);
    }
}

// Usage:
genericYiiLocation(function(success, data){
    if (!success) {
        //  Handle failure in here.
        return;
    } else {
        this = data;
        console.log("Got a longitude in callback: " + this.longitude);
    }
});