how can i wait for a google distance call to return my result before carrying on

Question

I am trying to figure out a way of initiating a google distancematrix call where i need to have the result returned before I can carry on with my program execution, using javascript and jquery. Please if anyone can help code sample idea. I have multiple legs for distances. ie: leg 1 start and finish point leg 2 start and finish point leg 3 start and finish point what i am trying to do is calc the travel time between the different legs, so leg 1 finishes driver needs to get to start of leg 2. so doing a call to get the distance between leg 1 finish and leg 2 start. Then moving on to the next calc. I already have the leg distances so, my code is as follows:

                var driving = 0;
            calculateDistances();

           code to work with the calculatedistances() result here


    function calculateDistances() {
 //alert(origin+','+destination);
 var service = new google.maps.DistanceMatrixService();
 service.getDistanceMatrix(
 {
  //set origin and destination points
  origins: [origin],//, origin2],
  destinations: [destination],          
  travelMode: google.maps.TravelMode.DRIVING,
  unitSystem: google.maps.UnitSystem.METRIC,
  avoidHighways: false,
  avoidTolls: false
  }, callback);
}

function callback(response, status) {
  if (status != google.maps.DistanceMatrixStatus.OK) {
     alert('Error was: ' + status);
  } else {
   var origins = response.originAddresses;
   var destinations = response.destinationAddresses;
   var outputDiv = '';
   for (var i = 0; i < origins.length; i++) {
     var results = response.rows[i].elements;
     //addMarker(origins[i], false);
     for (var j = 0; j < results.length; j++) {
        driving = parseFloat(results[j].distance.text); // driving is a script wide variable to hold the return value
     }
    }
}

}

Answer 1

Pass a callback into your calculateDistances() function, you can do it by passing in callback, and executing it with callback() at the end of the method. Call your function something else for clarity.

var driving = 0;
calculateDistances(callbackFunction);

function calculateDistances(callback) {

 var service = new google.maps.DistanceMatrixService();
 service.getDistanceMatrix(
 {
  //set origin and destination points
  origins: [origin],//, origin2],
  destinations: [destination],          
  travelMode: google.maps.TravelMode.DRIVING,
  unitSystem: google.maps.UnitSystem.METRIC,


avoidHighways: false,
  avoidTolls: false
  }, callback());
}

function callbackFunction(response, status) {
  if (status != google.maps.DistanceMatrixStatus.OK) {
}
//etc
}