Callback function returning undefined value

Question

I'm trying to use the Google Maps API to return the journey time and length from one point to another. Here is my code.

var routeInfoObject;

function findRoutes(given_origin, given_destination){
  var directionsService = new google.maps.DirectionsService();

  var directionsRequest = {
    origin: given_origin,
    destination: given_destination,
    travelMode: google.maps.DirectionsTravelMode.WALKING,
    unitSystem: google.maps.UnitSystem.METRIC,
    provideRouteAlternatives: true
  };

  var times = new Array();
  var lengths = new Array();
  var positions = new Array();
  directionsService.route(directionsRequest, function(response, status) {
      if (status == google.maps.DirectionsStatus.OK) {
         for (i = 0; i < response.routes.length && i < 4 ; i++) 
         {
             times[i] = response.routes[i].legs[0].duration.text;
             lengths[i] = response.routes[i].legs[0].distance.text;
         }

         routeInfoObject = times;
      } else { 
         console.log("There was an error with the request") 
      }
  });

  console.log(routeInfoObject);
}

The log at the bottom always returns undefined, even though routeInfoObject is a global variable and should be set to the value of times. Logging the value of times inside the callback function if I run findRoutes("longsight","rusholme") returns [18,18,18].

score 0 · Accepted Answer · answered Oct 25 '15 at 02:11

0

The callback function (function(response, status)) doesn't execute until after your console.log statement, so it's not assigned yet.

answered Oct 25 '15 at 02:11

Mark Brackett

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I'm confused, how can I fix this? Essentially I need to return a value from the callback to then be returned again from the findRoutes function. – RCarruthers Oct 25 '15 at 02:36
@user2952231 - you generally can't make an async api behave synchronously; you need to either pass a callback into findRoutes of what you want to do afterwards, or do a setTimeout/interval wait and check when routeInfoObject is no longer undefined. – Mark Brackett Oct 25 '15 at 03:21

Callback function returning undefined value

1 Answers1