AngularJS Overview Series - I

In this article you will learn about the concepts of AngularJS.

Introduction

The stand out hero in the market now. AngularJS it is from Google, thus intensifying the effectiveness of the plain HTML. There has been a constant and roaring buzz in the market on this. We have heard of MVC (Model-View-Controller), MVVM (Model-View-ViewModel) and many more frameworks. This is a simple JavaScript framework based on MVW framework.

MVW?

MVW

Ok, now what is MVW! It stands for Model-View-Whatever . Like Salman Khan says, Whatever you do man! So Angular says, Add Whatever you want man! The reason being is, it is actually close to MVC, MVVM and MVP as well. Earlier it had concepts related to MVC, but after the modification and enhancements and addition of the $scope, it came closer to MVVM framework as well. Thus, the framework became MVW. Before we start hand on Angular, we need to have the resources required by it and start experimenting in a normal text editor like Notepad++ or Sublime Text. So, is it time taking hectic? Not at all, just navigate now to Angular JS Resources, download and add the resources and just start. Even better way!! Just add the below CDN resources and start.

Some concepts

Now we have seen a lot of resources explaining the concepts that is new and interesting in AngularJS. Let us get a brief overview on each of the important concepts.

Angular Expressions

This is actually how Angular binds data onto the HTML and makes it dynamic in seconds. The syntax is {{ exp }}. Whatever is written in the braces, that data is bound to the HTML element.

  1. My age is: {{ 15 + 10 }}   

Output would be: My age is:25

This will display, My age is 25 in normal HTML as well. But one thing, please read further, only this will not let you display the evaluated value.

Angular directives

These are kinds of attributes added to the HTML elements, thus extending a new range of attributes to the HTML. ng- is the attribute syntax, just like data- attributes. There are flexibility in the directives as well. There are few in-build directives and there are directives we can create explicitly. Few of them are listed below along with a detailed example of their usage. Let's follow:
  • First and foremost directive is ng-app: This is utmost important directive as it starts/initiates the Angular application inside the HTML. If we remove the ng-app directive then the evaluation will fail as the Angular will not initiate.

  • ng-model: This is another important directive which actually makes our HTML dynamic as it stores the data/handles the data for the form or HTML controls which we add in the web pages.

  • ng-init: This is responsible to initiate the data for the model properties, in order to have some values pre-populated.
Let's have a look at a simple code snippet:
  1. <div ng-app="">  
  2. <input type="text" ng-model="firstName">  
  3. <input type="text" ng-model="lastName">  
  4. <span>{{firstName}} {{lastName}}</span> 
Here the ng-model binds the firstName and the lastName as you type in the text box to give a dynamic feel. To make the default names appear on the screen on the page load, we can use the ng-init to initiate the data for the model, just like below:
  1. <div ng-app="" ng-init="firstName='Suraj';lastName='Sahoo'">  
  2. <input type="text" ng-model="firstName">  
  3. <input type="text" ng-model="lastName">  
  4. <span>{{firstName}} {{lastName}}</span>  
  5. </div>  
AngularJS - MVC

AngularJS, as we mentioned above follows MVC architecture in the background. We saw in the above simple snippets, how the data is bound to the view from the model values and presented on the UI.

Controller

Thus when the event is fired the Angular Controller is responsible to fetch the data from http services using the $http.get(url) which in turn then binds data to the model using the ng-model and then data is dynamically bound to the view / html element. The concept here is similar and we will learn more on this once we follow up with the controllers and modules in Angular.

Conclusion

This was all about the start and simple directives to get your hands on AngularJS. In the succeeding modules and blogs, we will discuss more in detail.
 
Hands On Snippet
 
Try out the following simple snippet directly on any notepad, save as HTML and see the magic. 
  1. <html>  
  2. <script src="http://ajax.googleapis.com/ajax/libs/angularjs/1.4.8/angular.min.js"></script>  
  3. <body>  
  4. <h2>Welcome To Angular World</h2>
  5. <div ng-app="">  
  6. <label>First Name</label><br>  
  7. <input type="text" ng-model="firstName"><br>  
  8. <label>Last Name</label><br>  
  9. <input type="text" ng-model="lastName"><br><br>
  10. <span> Your Name is:-  {{firstName}} {{lastName}}</span>  
  11. </div>  
  12. </body>  
  13. </html>  
What's Next
  • Modular approach: Creating Modules in Angular ng-module.
  • Controllers in Angular ng-controller.
  • Scope in Angular $scope.
  • Server interaction and binding data from APIs in MVC & Http Services $http.