How to load JSON file from Thingworx Repository

Yes this seems to be difficult to achieve. I think in your code is a problem with passing arguments between the call of the service and the event. It is  correctly as your mentionded that this is asynchronous call – but nearly all calls in JavaScript are asynchronous calls. The $broadcast works asynchronously and will not return any values and there is no  way to pass e.g. the key argument to the event LoadJSON-complete. 

Also, I want to point that  to define the event listener inside the forEach loop is definitely not a good idea. The event listener should be defined globally.

So I fixed the code  and called the broadcast /also alternate call is twx.app.fn.triggerDataService (better) / - called the service in a loop for each key/value pair from  the json list . So all calls are executed immediately (as expected) - An then after some time the events are fired- but there seems to be something a twx srv cache  issue  - so it seems to forget the other call - when we have more than 2 or 3 call so it did not emit the events for all calls. 

To the question - how to make synchronous - I do not think that it is possible here.  In generally we can use some promise approach but here we have an array as results and it will be difficult to manage the different items

For me seems that the best approach is to use some recursive call principle - 

call - event completed - next call etc....

The following code was working fine in my example:

// $scope, $element, $attrs, $injector, $sce, $timeout, $http, $ionicPopup, and $ionicPopover services are available

$scope.modelDataDynamic=[];
$scope.COUNT=0;
 
var MODEL_JSON = {
 'model-1-a': 'a.json',
 'model-1-b': 'b.json',
 'model-1-c': 'c.json',
 'model-1-d': 'd.json',
 'model-1-e': 'e.json',
 'model-1-f': 'f.json',
}
//load MODEL_JSON files
console.log('load MODEL_JSON files');

//==================================================
//==================================================
angular.element(document).ready(function () {
 console.log("Register the LoadJson-Complete");
 //==== LoadJSON COMPLETE 
 $scope.$root.$on('LoadJSON-complete', function (event, args) {
 console.log("LoadJSON-complete event");
 //will print to console the event name - LoadJSON-Complete
 console.log("name=" + event.name)
 // the data was the event returns
 $scope.modelDataDynamic[$scope.COUNT].jsonData = args.data; 
 //print to the console to check the data
 console.log(JSON.stringify($scope.modelDataDynamic[$scope.COUNT].jsonData))
 // debugging inof
 console.log("key=" +$scope.modelDataDynamic[$scope.COUNT].key+";value="
 + $scope.modelDataDynamic[$scope.COUNT].value + ";COUNT="+$scope.COUNT+
 "length="+$scope.modelDataDynamic.length);
 // this a double check we will convert it to string and parse it back to json
 //this will ensure that data is correct and has the correct syntax
 if( ++$scope.COUNT > $scope.modelDataDynamic.length-1)
 {//finished
 $scope.finished(); 
 }
 else
 {$timeout($scope.GetJsonFromTwxRepository('/test/jsons/'
 + $scope.modelDataDynamic[$scope.COUNT].value),500,true) 
 }
 });
})
//===================================================
//==================================================
$scope.GetJsonFromTwxRepository = function (path) {
 console.log("$scope.GetJsonFromTwxRepository(path="+path+") ");
 $timeout(function () {
 // $rootScope.$broadcast('app.mdl.TestRepository.svc.LoadJSON',
 twx.app.fn.triggerDataService('TestRepository','LoadJSON',
 {"path": path});}
 , 5,true);
 console.log("after call of GetJsonFromTwxRepository")
};
//==================================================
//==================================================
$scope.$on('$ionicView.afterEnter', function () {
 console.log("$ionicView.afterEnter was called ");
 console.log('Calling now the service in a loop');
$scope.COUNT=0;
 angular.forEach(MODEL_JSON, function (value, key) {
 console.log("calling angular.forEach value="+value+ " key="+key);
 let temp_obj= {}
 temp_obj.key=key
 temp_obj.value=value
 $scope.modelDataDynamic.push(temp_obj) })
 
 $timeout(()=>{
 $scope.GetJsonFromTwxRepository('/test/jsons/' +$scope.modelDataDynamic[$scope.COUNT].value) 
 $scope.$applyAsync();
 },100,true)
})

//=======================$scope.finished();=========
//==================================================

//$scope.$watch('COUNT', function (newValue, oldValue, scope) {
 //if(scope.app.params.SVC_CALL_NUM <1)
$scope.finished=function(){ 
 
 console.warn("completed the loop");
 let a = $scope.modelDataDynamic
 for (var i in a) 
 { console.log("here Json for $scope.modelDataDynamic["+i+"]")
 console.log("key="+ a[i].key + " value="+a[i].value)
 console.log("==============================================")
 console.log(JSON.stringify(a[i].jsonData));
 console.log("==============================================")
 
} 
 $timeout( function() { console.warn($scope.modelDataDynamic);}, 1000)
}

So when tested I was working fine with the following print: