Loopback Callback inside For-Loop

Question

In a for-loop I call a loopback function (model.find()) and use the callback method. In this method I need the i variable of the for-loop to specify a variable but it is not accessible from closure. I already tried writing (i) or call(this,i) behind the callback function but it didn't work.

for (var i = 0; i < $scope.objects.length; i++) {
                    Priority.find({
                        filter: {
                            where: {priority: $scope.selectedPriority[i].priority}
                        }
                    }, function (prios) {
                            Priority.create({"priority": $scope.selectedPriority[i].priority //i is not accessible
                            }, function (priority) {
                                $scope.selectedPriority[i].priority = undefined; //i is not accessible
                            }, function (error) {
                                console.log(error);
                            });
                        }
                    });

        }

Answer 1

Actually "i" should be defined but you'll always find it at its highest value (= $scope.objects.length - 1), the reason is that since Priority.find is asynchronous, once it returns an answer, the for loop has already done iterating.

To solve it, you could put body of the loop inside a function:

 function find(i) {
    Priority.find({
                            filter: {
                                where: {priority: $scope.selectedPriority[i].priority}
                            }
                       }, function (prios) {
                               Priority.create({"priority": $scope.selectedPriority[i].priority //i is not accessible
                               }, function (priority) {
                                  $scope.selectedPriority[i].priority = undefined; //i is not accessible
                              }, function (error) {
                                 console.log(error);
                              });
                         }
                      });
}

So then, the for loop becomes:

for (var i = 0; i < $scope.objects.length; i++) {
    find(i);
}

essentially, you're "capturing" the value of "i" and send it as a function argument, as long as you're in the context of a specific function call, i stays fixed.