Keep waiting for loop increment until not getting function response

Question

I have a for loop and inside that I am calling one function. But before function response for loop variable is incremented by 1. I just want to wait until the response has come, then increment var by 1.

Here is my code:

    for(var i=0;i<$scope.latitude.length;i++)
        {
              console.log("inside for :",$scope.latitude[i]);
              console.log("i after for:" ,i);
            console.log("count before if:" ,count);
                   if($scope.latitude[i]!=1)
                   {

                        console.log("inside if count is :",count);
                        console.log("i inside if:" ,i);
                            var lat =$scope.latitude[i];
                            var lng=$scope.longitude[i];

                       console.log("lat is going",lat);
                       console.log("lng is going",lng);



                        $scope.getDistance(lat,lng).then(function(response,flag){
                        console.log("flag is" ,flag);

                      setTimeout(function(){

                               flag="true";


                      },1000);

                var results = response.rows[0].elements;

                console.log(results[0].distance.text);
                console.log(results[0].duration.text);
                 return results[0].distance.text 


            }).done(function(distanceMatrixResult,flag) {
                    console.log("flag inside done is:" ,flag);

                      console.log("count is ",count);
                    console.log("i inside done:" ,i);
                     console.log(distanceMatrixResult);
         $scope.clients.treasureHunts[count].distance =distanceMatrixResult;   


                  $ionicLoading.hide();

                console.log("Results:->>>>>>>>>>>>", JSON.stringify( $scope.clients));

})

$scope.getDistance=function(lat,lng){
       console.log("lat inside google distance function:-" ,lat);
           console.log("lng inside google distance function:-" ,lng);

            var service = new google.maps.DistanceMatrixService();


        $scope.destinationDetails = {
            lat: lat,
            lng: lng
            }

            console.log("destination:-" ,JSON.stringify(  $scope.destinationDetails.lat));
         console.log("destination:-" ,JSON.stringify(  $scope.destinationDetails.lng));
           //getting current location
               var onSuccess = function (position) {

             console.log('Current Position: ', position.coords.latitude, ',', position.coords.longitude);
             $scope.originCenter = {

                lat: position.coords.latitude,
                lng: position.coords.longitude

            };
                        geocodeLatLng($scope.originCenter);
               }

               function onError(error) {
            console.error('code: ' + error.code + '\n' + 'message: ' + error.message + '\n');
            //alert('Error Occured' + error.message);
        }
        navigator.geolocation.getCurrentPosition(onSuccess, onError);/////////---------------------------------


              function geocodeLatLng(originCenter) {
                 console.log("destination inside function:-" ,JSON.stringify(  $scope.destinationDetails.lat));
         console.log("destination inside function:-" ,JSON.stringify(  $scope.destinationDetails.lng));


            $scope.originDetails = new google.maps.LatLng(originCenter.lat, originCenter.lng);
            console.log('Origin Details: ',JSON.stringify($scope.originDetails));
            $scope.finalDestination = new google.maps.LatLng($scope.destinationDetails.lat, $scope.destinationDetails.lng);
            console.log('destination details: ', JSON.stringify($scope.finalDestination));

            service.getDistanceMatrix(

                {
                    origins: [$scope.originDetails],
                    destinations: [$scope.finalDestination],
                    travelMode: google.maps.TravelMode.DRIVING,
                    unitSystem: google.maps.UnitSystem.METRIC,
                    avoidHighways: false,
                    avoidTolls: false
                },
                function (response, status) {
                    if (status !== google.maps.DistanceMatrixStatus.OK) {

                       console.error(JSON.stringify(response));
                       d.reject(response);



                    } else {
                        console.log("returning response ",JSON.stringify(response));
                        var flag="true";


                    d.resolve(response,flag);




                    }           


         });

Just to make it clear, you only want to increment the value of i after the function `getDistance` returns a value, correct? — Satej S, Jan 21 '16 at 09:16
yes i want to incrment the value of i when i will get response from function that i called — Ashish Sinha, Jan 21 '16 at 09:18
If getDistance is an async function, then increment in the callback — mplungjan, Jan 21 '16 at 09:21
It's a for loop, it doesn't really make a difference between before and after the function is called.Your for loop variable is going to change at each iteration. If you want to use another variable, i'd suggest you create one explicitly — Satej S, Jan 21 '16 at 09:22
Check this out if the function is doing an async operation. http://stackoverflow.com/questions/1478295/what-does-async-false-do-in-jquery-ajax — NoviceLearner, Jan 21 '16 at 09:28

score 0 · Answer 1 · answered Jan 21 '16 at 10:07

Since js is single threaded (as far as regarded here) there can not be a loop waiting for something other happening in js code (like any callbacks executed..).

Looping over asynchronous calls need to split functionality into the async callback/success-handler (add some error handling as well;), e.g. like this:

function makeNextCall(i, total, onCompleted) {

  if( i >= total) {
    onCompleted();               // signal completion of whole iteration
  } else {
   makeAsyncCall(i, {                        // make the asynchronous call
     onSuccess : function() {                // define callback
      makeNextCall(i+1, total, onCompleted); // next iteration
    }
   }); 
  }
}

Keep waiting for loop increment until not getting function response

1 Answers1