Category Archives: JavaScript

Tricky behavior of AngularJS $resource service.

When using $resource service of AngularJS in one of the projects recently, i faced a tricky problem and thought it may be valuable to share the solution here.

 

Namely, one of the back-end services is returning an Array of String values like this, when making a GET call using a REST client:

[
  "Value_1",
  "Value_2",
  "Value_3",
  (...)
]

 

Having a standard AngularJS service defined like this:

angular.module('myAppBackendService', ['ngResource'])
  .factory('BackendApi', ['$resource', 'BackendHost', 'BackendPort', 'BackendVersion',
    function ($resource, BackendHost, BackendPort, BackendVersion) {
      var connString = BackendHost + ':' + BackendPort + '/' + BackendVersion;
      return {
        values: $resource(connString + '/values/:id',
        {
          id:'@id'
        }, {
          query: {method: 'GET', isArray: true},
          get: {method: 'GET', params:{id:'@id'}, isArray: true},
          save: {method: 'POST', isArray: true}
        })
      };
  }]);

 

and invoked like this

$scope.values = BackendApi.values.get(
  function(value) {
    // do something interesting with returned values here
    $log.debug('Success: Calling the /values back-end service', value);
  },
  function(errResponse) {
    // do something else in case of error here
    $log.debug('Error: Calling the /values back-end service', errResponse);
  });

 

i was getting a successful response from the server, however the data format which i was getting was completely unexpected to me:

[
  {
    "0" : "V",
    "1" : "a",
    "2" : "l",
    "3" : "u",
    "4" : "e",
    "5" : "_",
    "6" : "1"
  },
  {
    "0" : "V",
    "1" : "a",
    "2" : "l",
    "3" : "u",
    "4" : "e",
    "5" : "_",
    "6" : "2"
  }
]

you can imagine my surprise when trying to figure out what the heck was wrong with it?

 

After spending some time trying to google out a solution, i finally found the reason for such behavior. Listen to this:

“…ngResource expects an object or an array of objects in your response”

“…When isArray is set to true in the list of actions, the ngResource module iterates over each item received in the response and it creates a new instance of a Resource. To do this Angular performs a deep copy between the item received and the Resource class, which gives us an object with special methods ($save$deleteand so on)”

“…Internally angular uses angular.copy to perform the deep copy and this function only operates with objects andarrays, when we pass a string, it will treat it like an object.

Strings in JS can behave as arrays by providing sequential access to each character. angular.copy will produce the following when passed a string

angular.copy('hi',{}) => {0:'h', 1:'i'}

Each character becomes a value in an object, with its index set as the key. ngResource will provide a resource with properties 0 and 1.”

 

 

So, what are the possible solutions then?

  1. Use the “transformResponse” action of $resource service (you can read more about this in the documentation of the service itself, here)
  2. Use the lower level $http service:
    $http.get('/res').success(function(data){
      $scope.test = data;
    });
    
  3. Return an array of objects in your json response:
    [
      {'data': "hello"},
      {'data': "world"}
    ]
    

 

Happy coding!

 

 

 

 

Resources:

AngularJS custom HTTP headers in resource service

Recently i had to make an HTTP call from the browser (client-side) using JavaScript / AngularJS to a REST API (server-side) and retrieve data. Since the authentication mechanism of the API required a security token to be passed over with the request, i studied AngularJS specs on how to do it best. Basically, there are two ways to do it, either as a:

  1. query parameter, or
  2. custom HTTP header

 

Because i didn’t wanted the security token to appear anywhere in the logs or debugging console (like on the picture below, in case of making use of option 1 just mentioned, ie. query parameter), i decided on passing the token as a custom (there’s no standard header for passing tokens) HTTP header.

AngularJS query API token

 

Since i use Yeoman (app workflow/scaffolding tool) i noticed that through a standard angular-template used for generating an application scaffolding, you’re getting dependency on angular framework in version 1.0.7 (last stable version as of writing this post). Although this is what you would generally expect (stable version, not a snapshot), the problem is that angular documentation for $resource service (which is what i prefer to use over $http service), does not mention the possibility of sending HTTP headers (regarding $http – i think of it as a solution for rather “general purpose AJAX calls”).

 

One way to set HTTP headers is by accessing $httpProvider.defaults.headers configuration object, like this:

$httpProvider.defaults.headers.get['API-Token'] = 'vy4eUCqpQmGoeWsnHKwCQw'

(more documentation about that you’ll find here), but this way you’re modifying $httpProvider globally which may not be what you exactly want.

 

Google search came with help and i found issue 736, which acknowledges that “$resource should support custom http headers”, but it is with the (unstable) release 1.1.3 where this feature is supported for sure (maybe earlier “unstable” versions do support it too, haven’t checked that actually, but definitely none of the stable versions do, as of today).

 

So, what is it that you have to do in order to introduce an unstable version of AngularJS into your project managed by Bower?

bower install angular-unstable
bower install angular-resource-unstable

(dependency on angular-resource.js is required in order for it to work).

 

Now, the only other thing left to do is to update your index.html file accordingly (to make use of proper version of libraries) :

<script src="bower_components/angular-unstable/angular.js"></script>
<script src="bower_components/angular-resource-unstable/angular-resource.js"></script>

 

…and you can start adding custom HTTP headers in your code:

angular.module('usersService', ['ngResource'])
    .factory('User', function($resource, api-token) {
        var User = $resource('http://api.test.com\\:8080/1.0/users', { }, {
            query: {
                method: 'GET',
                isArray: true,
                headers: { 'API-Token': api-token }
            }
        });
        return User
    });

 

Hope this short post will save some of your time 🙂 Cheers!

 

 

Resources:

AngularJS, Karma and debugging unit tests in WebStorm or IntelliJ IDEA

Recently i had to debug few Javascript unit tests in WebStorm IDE and was wondering if it’ll be as easy of an experience as it is in case of Java and IntelliJ IDEA (where i originally come from).

WebStorm 6 doesn’t offer native Karma test runner support (ver 7 which is currently in EAP, does – details here), but using a NodeJS plug-in you can execute any kind of NodeJS application (Karma included).

 

OK, what we’ll need in this exercise is following:

  • One of two JetBrains IDE’s, either:
    • WebStorm (great for JavaScript code) or
    • IntelliJ IDEA (Java’s no. 1 IDE)
  • NodeJS plug-in installed in the IDE:
    • WebStorm comes having it already pre-installed
    • in case of IDEA (Ultimate version, because Community Edition doesn’t have the required JavaScript plug-in for it to work, see here) the plug-in can be downloaded from here.
  • NodeJS environment which can be downloaded from here.
  • Karma (old name Testacular) test runner installed (“npm install -g karma”) that allows running unit (or E2E) tests in one of these browsers:
    • Chrome
    • ChromeCanary
    • Firefox
    • Opera
    • Safari (only Mac)
    • PhantomJS
    • IE (only Windows)
  • Chrome/Firefox “JetBrains IDE Support” extension (required for debugging) that can be downloaded from here.

 

Installing the NodeJS plug-in in IntelliJ IDEA:

  • Open “Settings” dialog (File -> Settings… in the menu bar)
  • Select “Plugins” (under “IDE Settings”)
  • Click “Browse repositories…”
  • Click “Download and Install” on the “NodeJS” plug-in
  • Press “Restart” when asked, to restart the IDE

 

Configuring IDE to execute Karma test in NodeJS using the plug-in:

  • Open the Run/Debug Configuration dialog by selecting “Edit Configurations” in the Run area of the main toolbar of WebStorm.
  • Add the following two configurations (picture below):
    • “Karma Run”: to perform a “single run” of your unit tests.
    • “Karma Server”: to start Karma in “Continuous Integration” mode (automatic re-runs of your tests whenever files change).
  • Configure the “Karma Run” configuration:
    • Press the “+” button in the top-left of the “Run/Debug Configurations” dialog.
    • Select “Node.js” in the list
    • Fill in the following fields:
      • Name: enter “Karma Run”
      • Path to Node: absolute path to NodeJS executable (i.e. “c:\NodeJS\node.exe”)
      • Working Directory: absolute path of your AngularJS application (i.e. “C:\MyProjects\AngularApp”)
      • Path to Node App JS File: Should point to the (globally, ie. -g) installed “Karma” NodeJs executable (i.e. “C:\Users\…\AppData\Roaming\npm\node_modules\karma\bin\karma”)
      • Application Parameters: run karma.conf.js –single-run –no-auto-watch –reporters dots
    • Press “Apply”
  • Configure the “Karma Server” configuration:
    • Essentially take the same steps as while configuring “Karma Run”, changing only the following:
      • Name: enter “Karma Run”
      • Application Parametersstart karma.conf.js –no-single-run –auto-watch –reporters dots
  • Configure the “Karma Debug” configuration to allow debugging of Karma unit tests
    • Press the “+” button in the top-left of the “Run/Debug Configurations” dialog.
    • Select “JavaScript Debug -> Remote” in the list
    • Fill in the following fields:
      • Name: enter “Karma Debug”
      • URL to openhttp://localhost:8100/debug.html (port number depends on your configuration in karma.conf.js file (passed as an “Application Parameter” in the previous two configurations)
      • Browser: chose either Chrome or Firefox
      • Set the “Remote URL” field to point to “http://localhost:8100/base

        Karma Debug configuration in IntelliJ WebStorm

 

Finally, run your “Karma Server” configuration and while it’s working in the background (–auto-watch mode), set debugging breakpoints in your code and fire “Karma Debug” configuration.

That’s it. Hope this small guide turns out to be helpful.

 

Resources: