How do I return a variable from Google Maps JavaScript geocoder callback?

Question

I am working with the google maps API and whenever I return the variable to the initialize function from the codeLatLng function it claims undefined. If I print the variable from the codeLatLng it shows up fine.

  var geocoder;
  function initialize() {
    geocoder = new google.maps.Geocoder();
    var latlng = new google.maps.LatLng(40.730885,-73.997383);
    var addr = codeLatLng();
    document.write(addr);

  }

  function codeLatLng() {
    var latlng = new google.maps.LatLng(40.730885,-73.997383);
    if (geocoder) {
      geocoder.geocode({'latLng': latlng}, function(results, status) {
        if (status == google.maps.GeocoderStatus.OK) {
          if (results[1]) {
                return results[1].formatted_address;
          } else {
            alert("No results found");
          }
        } else {
          alert("Geocoder failed due to: " + status);
        }
      });
    }
  }

prints out undefined

If I do:

  var geocoder;
  function initialize() {
    geocoder = new google.maps.Geocoder();
    var latlng = new google.maps.LatLng(40.730885,-73.997383);
    codeLatLng();


  }

  function codeLatLng() {
    var latlng = new google.maps.LatLng(40.730885,-73.997383);
    if (geocoder) {
      geocoder.geocode({'latLng': latlng}, function(results, status) {
        if (status == google.maps.GeocoderStatus.OK) {
          if (results[1]) {
                document.write(results[1].formatted_address);
          } else {
            alert("No results found");
          }
        } else {
          alert("Geocoder failed due to: " + status);
        }
      });
    }
  }

prints out New York, NY 10012, USA

Answer 1

You can't return the value from the function, the value doesn't exist yet when the function returns.

The geocode method makes an asynchonous call and uses a callback to handle the result, so you have to do the same in the codeLatLng function:

var geocoder;
function initialize() {
  geocoder = new google.maps.Geocoder();
  var latlng = new google.maps.LatLng(40.730885,-73.997383);
  codeLatLng(function(addr){
    alert(addr);
  });
}

function codeLatLng(callback) {
  var latlng = new google.maps.LatLng(40.730885,-73.997383);
  if (geocoder) {
    geocoder.geocode({'latLng': latlng}, function(results, status) {
      if (status == google.maps.GeocoderStatus.OK) {
        if (results[1]) {
          callback(results[1].formatted_address);
        } else {
          alert("No results found");
        }
      } else {
        alert("Geocoder failed due to: " + status);
      }
    });
  }
}