AngularJS - Overview

AngularJS is an open-source web application framework. It was originally developed in 2009 by Misko Hevery and Adam Abrons. It is now maintained by Google. Its latest version is 1.2.21.

Definition of AngularJS as put by its official documentation is as follows:

AngularJS is a structural framework for dynamic web applications. It lets you use HTML as your template language and lets you extend HTML's syntax to express your application components clearly and succinctly. Its data binding and dependency injection eliminate much of the code you currently have to write. And it all happens within the browser, making it an ideal partner with any server technology.

General Features

The general features of AngularJS are as follows:

• AngularJS is a efficient framework that can create Rich Internet Applications (RIA).
• AngularJS provides developers an options to write client side applications using JavaScript in a clean Model View Controller (MVC) way.
• Applications written in AngularJS are cross-browser compliant. AngularJS automatically handles JavaScript code suitable for each browser.
• AngularJS is open source, completely free, and used by thousands of developers around the world. It is licensed under the Apache license version 2.0.

Overall, AngularJS is a framework to build large scale, high-performance, and easy-to-maintain web applications.

Core Features

The core features of AngularJS are as follows:

• Data-binding: It is the automatic synchronization of data between model and view components.
• Scope: These are objects that refer to the model. They act as a glue between controller and view.
• Controller: These are JavaScript functions bound to a particular scope.
• Services: AngularJS comes with several built-in services such as $http to make a XMLHttpRequests. These are singleton objects which are instantiated only once in app.
• Filters: These select a subset of items from an array and returns a new array.
• Directives: Directives are markers on DOM elements such as elements, attributes, css, and more. These can be used to create custom HTML tags that serve as new, custom widgets. AngularJS has built-in directives such as ngBind, ngModel, etc.
• Templates:These are the rendered view with information from the controller and model. These can be a single file (such as index.html) or multiple views in one page using partials.
• Routing: It is concept of switching views.
• Model View Whatever: MVW is a design pattern for dividing an application into different parts called Model, View, and Controller, each with distinct responsibilities. AngularJS does not implement MVC in the traditional sense, but rather something closer to MVVM (Model-View-ViewModel). The Angular JS team refers it humorously as Model View Whatever.
• Deep Linking: Deep linking allows to encode the state of application in the URL so that it can be bookmarked. The application can then be restored from the URL to the same state.
• Dependency Injection: AngularJS has a built-in dependency injection subsystem that helps the developer to create, understand, and test the applications easily.

Concepts

The following diagram depicts some important parts of AngularJS which we will discuss in detail in the subsequent chapters.

Advantages of AngularJS

The advantages of AngularJS are:

• It provides the capability to create Single Page Application in a very clean and maintainable way.
• It provides data binding capability to HTML. Thus, it gives user a rich and responsive experience.
• AngularJS code is unit testable.
• AngularJS uses dependency injection and make use of separation of concerns.
• AngularJS provides reusable components.
• With AngularJS, the developers can achieve more functionality with short code.
• In AngularJS, views are pure html pages, and controllers written in JavaScript do the business processing.

On the top of everything, AngularJS applications can run on all major browsers and smart phones, including Android and iOS based phones/tablets.

Disadvantages of AngularJS

Though AngularJS comes with a lot of merits, here are some points of concern:

• Not secure : Being JavaScript only framework, application written in AngularJS are not safe. Server side authentication and authorization is must to keep an application secure.
• Not degradable: If the user of your application disables JavaScript, then nothing would be visible, except the basic page.

AngularJS Directives

The AngularJS framework can be divided into three major parts:

• ng-app : This directive defines and links an AngularJS application to HTML.
• ng-model : This directive binds the values of AngularJS application data to HTML input controls.
• ng-bind : This directive binds the AngularJS application data to HTML tags.

Angular JS Browser support

he latest version of AngularJS 1.3 support Safari, Chrome, Firefox, Opera 15+, IE9+ and mobile browsers (Android, Chrome Mobile, iOS Safari, Opera Mobile).

AngularJS 1.3 has dropped support for IE8 but AngularJS 1.2 will continue to support IE8.

AngularJS Developmet IDE

AngularJS development can be done with the help of following IDEs.

1. Visual Studio 2012, 2013, 2015 or higher
2. Eclipse
3. WebStorm
4. Sublime Text
5. TextMate

Why this is called AngularJS

Html has angle brackets i.e. <,> and ng sound like Angular. That’s why it is called AngularJS

Why Angular JS?

There are numerous of reasons to choose AngularJS as you web development framework. Some of them are listed below:

1. It is based on MVC pattern which helps you to properly organize your web apps or web application.
2. It extends HTML by attaching directives to your HTML markup with new attributes or tags and expressions in order to define very powerful templates.
3. It also allows you to create your own directives, crafting reusable components that fill your needs and abstracting away all the DOM manipulation logic.
4. It supports two-way data binding i.e. connects your HTML (views) to your JavaScript objects (models) seamlessly. In this way your model will be immediately reflected into your view without the need for any DOM manipulation or event handling (with jQuery).
5. It encapsulates the behavior of your application in controllers which are instantiated with the help of dependency injection.
6. It supports services that can be injected into your controllers to use some utility code to fulfill your need.
   For example, it provides $http service to communicate with REST service.
7. It helps you to structure and test your JavaScript code very easily.
8. Also, AngularJS is mature community to help you. It has widely support over the internet.

AngularJS

AngularJS is an open-source JavaScript framework developed by Google. It helps you to create single-page applications or one-page web applications that only require HTML, CSS, and JavaScript on the client side. It is based on MV-* pattern and allow you to build well structured, easily testable, and maintainable front-end applications.

AngularJS has changed the way to web development. It is not based on jQuery to perform its operations. In spite of using ASP.NET Web form, ASP.NET MVC, PHP, JSP, Ruby on Rails for web development, you can do your complete web development by using most powerful and adaptive JavaScript Framework AngularJS. There is no doubt, JavaScript frameworks like AngularJS, Ember etc. are the future of web development.

Difference Between Constant and ReadOnly and Static

Constant and ReadOnly keyword are used to make a field constant which value cannot be modified. Static keyword is used to make members static that can be shared by all the class objects. In this article, I am going to explain the difference among these three.

Constant

Constant fields or local variables must be assigned a value at the time of declaration and after that they cannot be modified. By default constant are static, hence you cannot define a constant type as static.

public const int X = 10;

A const field is a compile-time constant. A constant field or local variable can be initialized with a constant expression which must be fully evaluated at compile time.

void Calculate(int Z)
{
 const int X = 10, X1 = 50;
 const int Y = X + X1; //no error, since its evaluated a compile time
 const int Y1 = X + Z; //gives error, since its evaluated at run time
}

You can apply const keyword to built-in value types (byte, short, int, long, char, float, double, decimal, bool), enum, a string literal, or a reference type which can be assigned with a value null.

const MyClass obj1 = null;//no error, since its evaluated a compile time
const MyClass obj2 = new MyClass();//gives error, since its evaluated at run time

Constants can be marked as public, private, protected, internal, or protected internal access modifiers.

Use the const modifier when you sure that the value a field or local variable would not be changed.

ReadOnly

A readonly field can be initialized either at the time of declaration or with in the constructor of same class. Therefore, readonly fields can be used for run-time constants.

class MyClass
{
 readonly int X = 10; // initialized at the time of declaration
 readonly int X1;
 
 public MyClass(int x1)
 {
 X1 = x1; // initialized at run time
 }
}

Explicitly, you can specify a readonly field as static since, like constant by default it is not static. Readonly keyword can be apply to value type and reference type (which initialized by using the new keyword) both. Also, delegate and event could not be readonly.

Use the readonly modifier when you want to make a field constant at run time.

Static

The static keyword is used to specify a static member, which means static members are common to all the objects and they do not tied to a specific object. This keyword can be used with classes, fields, methods, properties, operators, events, and constructors, but it cannot be used with indexers, destructors, or types other than classes.

class MyClass
{
 static int X = 10;
 int Y = 20;
 public static void Show()
 {
 Console.WriteLine(X);
 Console.WriteLine(Y); //error, since you can access only static members
 }
}

Key points about Static keyword

1. If the static keyword is applied to a class, all the members of the class must be static.
2. Static methods can only access static members of same class. Static properties are used to get or set the value of static fields of a class.
3. Static constructor can't be parameterized and public. Static constructor is always a private default constructor which is used to initialize static fields of the class.