Now it's time to make the web page dynamic — with AngularJS. We'll also add a test that verifies the code for the controller we are going to add.

There are many ways to structure the code for an application. For Angular apps, we encourage the use of the Model-View-Controller (MVC) design pattern to decouple the code and to separate concerns. With that in mind, let's use a little Angular and JavaScript to add model, view, and controller components to our app.

The app now contains a list with three phones.

The most important changes are listed below. You can see the full diff on GitHub:

View and Template

In Angular, the view is a projection of the model through the HTML template. This means that whenever the model changes, Angular refreshes the appropriate binding points, which updates the view.

The view component is constructed by Angular from this template:

app/index.html:

<html ng-app>
<head>
  ...
  <script src="lib/angular/angular.js"></script>
  <script src="js/controllers.js"></script>
</head>
<body ng-controller="PhoneListCtrl">

  <ul>
    <li ng-repeat="phone in phones">
      {{phone.name}}
      <p>{{phone.snippet}}</p>
    </li>
  </ul>
</body>
</html>

We replaced the hard-coded phone list with the ngRepeat directive and two Angular expressions enclosed in curly braces: {{phone.name}} and {{phone.snippet}}:

The ng-repeat="phone in phones" statement in the <li> tag is an Angular repeater. The repeater tells Angular to create a <li> element for each phone in the list using the first <li> tag as the template.
As we've learned in step 0, the curly braces around phone.name and phone.snippet denote bindings. As opposed to evaluating constants, these expressions are referring to our application model, which was set up in our PhoneListCtrl controller.

Model and Controller

The data model (a simple array of phones in object literal notation) is instantiated within the PhoneListCtrl controller:

app/js/controllers.js:

function PhoneListCtrl($scope) {
  $scope.phones = [
    {"name": "Nexus S",
     "snippet": "Fast just got faster with Nexus S."},
    {"name": "Motorola XOOM™ with Wi-Fi",
     "snippet": "The Next, Next Generation tablet."},
    {"name": "MOTOROLA XOOM™",
     "snippet": "The Next, Next Generation tablet."}
  ];
}

Although the controller is not yet doing very much controlling, it is playing a crucial role. By providing context for our data model, the controller allows us to establish data-binding between the model and the view. We connected the dots between the presentation, data, and logic components as follows:

PhoneListCtrl — the name of our controller function (located in the JavaScript file controllers.js), matches the value of the ngController directive located on the <body> tag.
The phone data is then attached to the scope ($scope) that was injected into our controller function. The controller scope is a prototypical descendant of the root scope that was created when the application bootstrapped. This controller scope is available to all bindings located within the <body ng-controller="PhoneListCtrl"> tag.

The concept of a scope in Angular is crucial; a scope can be seen as the glue which allows the template, model and controller to work together. Angular uses scopes, along with the information contained in the template, data model, and controller, to keep models and views separate, but in sync. Any changes made to the model are reflected in the view; any changes that occur in the view are reflected in the model.

To learn more about Angular scopes, see the angular scope documentation.

Tests

The "Angular way" makes it easy to test code as it is being developed. Take a look at the following unit test for your newly created controller:

test/unit/controllersSpec.js:

describe('PhoneCat controllers', function() {

  describe('PhoneListCtrl', function(){

    it('should create "phones" model with 3 phones', function() {
      var scope = {},
          ctrl = new PhoneListCtrl(scope);

      expect(scope.phones.length).toBe(3);
    });
  });
});

The test instantiates our PhoneListCtrl and verifies that its phones array property contains three records. This example demonstrates how easy it is to create a unit test for code in Angular. Since testing is such a critical part of software development, we make it easy to create tests in Angular so that developers are encouraged to write them.

Angular developers prefer the syntax of Jasmine's Behavior-driven Development (BDD) framework when writing tests. Although Angular does not require you to use Jasmine, we wrote all of the tests in this tutorial in Jasmine. You can learn about Jasmine on the Jasmine home page and on the Jasmine wiki.

The angular-seed project is pre-configured to run all unit tests using Karma. To run the test, do the following:

In a separate terminal window or tab, go to the angular-phonecat directory and run ./scripts/test.sh to start the Karma server (the config file necessary to start the server is located at ./config/karma.conf.js).
Karma will start a new instance of Chrome browser automatically. Just ignore it and let it run in the background. Karma will use this browser for test execution.

You should see the following or similar output in the terminal:

      info: Karma server started at http://localhost:9876/
      info (launcher): Starting  browser "Chrome"
      info (Chrome 22.0): Connected on socket id tPUm9DXcLHtZTKbAEO-n
      Chrome 22.0: Executed 1 of 1 SUCCESS (0.093 secs / 0.004 secs)

Yay! The test passed! Or not...

To rerun the tests, just change any of the source or test files. Karma will notice the change and will rerun the tests for you. Now isn't that sweet?

Experiments

Add another binding to index.html. For example:

    <p>Total number of phones: {{phones.length}}</p>

Create a new model property in the controller and bind to it from the template. For example:
```
    $scope.hello = "Hello, World!"
```
Refresh your browser to make sure it says, "Hello, World!"

Create a repeater that constructs a simple table:

    <table>
      <tr><th>row number</th></tr>
      <tr ng-repeat="i in [0, 1, 2, 3, 4, 5, 6, 7]"><td>{{i}}</td></tr>
    </table>

Now, make the list 1-based by incrementing i by one in the binding:

    <table>
      <tr><th>row number</th></tr>
      <tr ng-repeat="i in [0, 1, 2, 3, 4, 5, 6, 7]"><td>{{i+1}}</td></tr>
    </table>

Make the unit test fail by changing the toBe(3) statement to toBe(4).

Summary

You now have a dynamic app that features separate model, view, and controller components, and you are testing as you go. Now, let's go to step 3 to learn how to add full text search to the app.