AngularJS service injection based on feature detection

Question

In my Angular app, I need to create a persistence service interface that calls a concrete implementation based on the persistence mechanisms available in my browser. I am thinking of implementing this using a generic storageService that calls a specific storageService that understands a storage mechanism.

For example, the generic storageService will provide the following interface:

angular
    .module('app.storage')
    .factory('storageService', storageService);

function storageService() {
    return {
        saveItem: saveItem,
        getItem: getItem
    }

    ...
}

There will be multiple implementations of the storageService, e.g. localStorageService, indexedDbStorageService, webSqlStorageService.

What is the best way to dynamically inject a concrete storage service based on browser features. For example,

if (isWebSqlAvailable()) {
    // inject webSqlStorageService 
}
else if (isIndexedDbAvailable() {
    // inject indexedDbStorageService 
}
else if (isLocalStorageAvailable() {
    // inject localStorageService 
}

Answer 1

angular
  .module('app.storage')
  .factory('storageService', ['$injector', storageService]);

  function storageService($injector) {

  var svc;
  if (isWebSqlAvailable()) {
    svc = $injector.get('webSqlService');
  }
  else if (isIndexedDbAvailable() {
    svc = $injector.get('indexedDbService');
  }
  else if (isLocalStorageAvailable() {
    svc = $injector.get('localStorageService');
  }

  return svc;
}


angular
  .module('app.storage').factory('webSqlService', webSqlService);

function webSqlService(){
   return {
      saveItem: saveItem,
      getItem: getItem
   }

   function getItem(){

   }

   function saveItem(){

   }

}

angular
  .module('app.storage').factory('indexedDbService', indexedDbService);

function indexedDbService(){
   return {
      saveItem: saveItem,
      getItem: getItem
   }

   function getItem(){

   }

   function saveItem(){

   }

}

And then, you will just have to inject your storageService everywhere you want.