AngularJS Tutorial

Introduction

AngularJS is a very powerful JavaScript Framework. It is used in Single Page Application (SPA) projects. It extends HTML DOM with additional attributes and makes it more responsive to user actions. AngularJS is open source, completely free, and used by thousands of developers around the world.

AngularJS is based on the MVC pattern (Model View Control). Therefore AngularJS separates your RIA application into models, views and controllers. The views are specified using HTML + AngularJS own template language. The models and controllers are specified via JavaScript objects and JavaScript functions.

A Model View Controller is a software design pattern for developing web applications.

• MVC is popular because it isolates the application logic from the user interface layer and supports the separation of concerns.
• The controller receives all requests for the application and then works with the model to prepare any data needed by the view.
• The view then uses the data prepared by the controller to generate a final presentable response.

Model: It is the lowest level of the pattern responsible for maintaining data.

View: It is responsible for displaying all or a portion of the data to the user.

Controller: It is a software Code that controls the interactions between the Model and View.

Angular Tutorial

As of 2020, every task is performed within an application. Hence, there is a huge demand for applications world-wide. There are many different applications being developed in the current era of living. The development of the applications has become a tedious task as it requires quality and customer satisfaction. It is required to use multiple frameworks that will help in meeting the customer and client requirements. Angular is one of the frameworks that is commonly used in most the organisations. It has become popular for its multiple features and advantages that account to become the best framework for developing applications. In this tutorial, you will gain an understanding of Angular, its features, architecture and components, lifecycle, advantages and disadvantages, etc.

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What is Angular?

Angular is referred to as one of the open-source frameworks that is helpful in building client-side web applications. Angular is based on the typescript which is a superset of JavaScript. You need to know about JavaScript in the first place.

JavaScript is an important aspect of web development that is designed to deal with dynamic content. The dynamic Content here refers to the frequent changing content or the changes that take place. The developers have started creating their own custom JavaScript library that is intended to minimise the number of lines in the code and also implement the functionalities that are complex. Angular came up later on as a client-side JavaScript framework that was specifically designed to provide extensible support to the developers in building single-page applications by following the different practices in web development.

There is a difference between the regular website and SPA. SPAs will have higher usage of ajax and the number of refreshes will be less. It is not the same in the case of a regular website.

In simple terms, Angular is referred to as the front-end web application platform and developed by the team at Google and also includes the community of corporations and individuals. Angular is different from AngularJs. Most of them will get confused that Angular and Angular Js are the same.

Why is Angular used?

There are many reasons why Angular has to be used for the development of applications. Few of the strong reasons are included or explained here. The great ecosystem of third-party components: 

There has been an increase in the demand for Angular and the popularity has then resulted in many different additional tools and components that can be further used in Angular applications. Hence it is also flexible to provide the additional functionalities and also the improvements in the production level.

Component-based architecture: Angular versions have been changing the conversions. Angular has performed a shift from MVC to a component-based architecture. As per the component-based architecture, the application is divided into the functional and logical components that are independent. It also provides us with flexibility so that the components can be replaced and decoupled as well so that they can also be used in the different other parts of the application. It also allows easy testing of the web application and also ensures that the application or the component is working as expected.

Detailed documentation: Angular maintains detailed documentation allowing the developers to find all the required information without interacting with any other people in the organisation. It is also providing the flexibility to developers to come up with solutions that would resolve the issues and also focus on the time frames.

Features of Angular

Angular has come up with multiple features which have brought a very high demand for the development of the applications. Below listed are the features of Angular which we all need to know.

1. High speed and optimum performance: Angular provides the flexibility and capability of redefining the modern JavaScript virtual machine by making changes to the templates in the code. Hence the handwritten code can be leveraged on the framework. Angular also allows you to render the code into CSS and HTML. It also allows you to view the application for the first time on any type of platform like .Net, PHP, etc.

It is also observed that the loading time that is taken for the applications that are built using Angular is faster when compared to the other front-end frameworks that are used for application development. It is said that the loading will take place as the speed of the cheetah and also allows the code to be split automatically based on the rendering requirements and also based on the user loading.

2. Cross platform: Angular is capable of helping in developing progressive web applications. It also allows you to deploy applications as progressive and also as a native. You are also allowed to build the applications for the desktop using the Angular.

3. Angular applications for everyone: Angular is referred to as a user-friendly platform that will help in creating the high end animations to improve and enhance the user experience. It is not only restricted for the web applications but also allows you to create the high end animations. The application programming interface of Angular is very intuitive which allows the users or the developers to include the animation as well with the less lines of code.It also provides the flexibility to fix the broken code any time by making use of the smart unit testing frameworks that are available in Angular.

4. Efficient two way data binding: Angular has come up with the two way data binding system. There exists a synchronisation between the view layer and the model layer and the view in layer will be exactly representing the model layer. If there are any Changes to the model or any modifications then the users will be able to see the same in the view model automatically. There will be a reduced development time.

5. Angular command line interface: The Angular command line interface is one of the best practices that is used for the printing development of the applications. There are two different command line interfaces: ng-add and ng-new.

6. Virtual scrolling: Angular has come up with the feature of virtual scrolling which will help the code to react to the different scroll events that take place. Apart from performing the loading and unloading of the DOM elements, virtual scrolling is referred to as the effective way that helps in performing the items simulation.

7. Dependency injection: Angular has come up with the dependency injection which is one of the most important features that is built in. This feature is making the application development easy for the developers. All it does is to ask for the dependencies.

8. MVC architecture: MVC usually refers to the model view controller. In MVC, the model is responsible for managing the application data while the view is responsible for managing the data display. The controller plays a role of the connector between the model and the view layers. In the MVC architecture, you are allowed to divide the app or split the app and the rest is performed on its own. This MVC architecture that is used in Angular helps in saving the coding time.

AngularJS Interview Questions

Architecture of Angular framework:

Angular is referred to as a framework that is responsible for building the client applications either in HTML or by using JavaScript. The designing can be performed by using the typescript that is  responsible for compiling to JavaScript. The Angular framework usually consists of the different set of libraries in which some of them will be optional and some will be core.

You will be making use of the HTML templates and writing the Angular applications and are used to markup, also writing the component classes specifically is used for managing the templates that you have composed. Then you will be binding the components and services in two different models launching applications by bootstrapping the root module.

Once the bootstrapping of the root module is completed, then Angular will be taking over and presenting the application in the browser and will also respond to the user interactions based on the instructions that you will be providing to the system.

The architecture diagram of Angular usually consists of eight building blocks in an Angular application. They are:

1. Modules 

2. Components

3. Templates

4. Metadata

5. Data binding

6. Directives 

7. Services 

8. Dependency injection.

Modules: Modules in Angular will be different from the complement JavaScript modules. Angular consists of an NgModule that will declare a compilation context that is defined for the set of the components which are  specifically dedicated to the application domain or a workflow. Every Angular application will maintain a root module which is normally named as AppModule. This root module will be providing a bootstrap mechanism that will be launching the application. There will be many different functional models in the Angular application. The NgModule is also responsible for importing the functionality from the other NgModules.

Components: There will be at least one component in every Android application. The root component is a component that will be connecting the component hierarchy with the page document object model also called as DOM. The component is used to define a class and it consists of the information like the application data and the logic. The component is associated with the HTML template which helps in defining the view that has to be displayed. There is one decorator called @Component() that is responsible for identifying the class immediately as a component and also providing the template. 

Templates, directives, and data binding: A Temperate is usually referred to as a combination of HTML and Angular markup which helps in modifying the HTML elements before they are displayed. 

The template directives consist of the information like the programming logic and binding information markup connecting the application data and Document Object Model. Data binding is represented in two different ways or types. They are: Property binding and event binding 

The event binding is responsible for allowing the app to respond to the input of the user by updating the application data. 

The property binding is responsible for letting the interpolated values that have been computed from your application data into the HTML.

Services and Dependency injection: You will be creating the service class when you want to share the data or the logic to the specific components for the logic of the data that is not associated with any sort of specific view. The service class definition will be preceded by the @Injectable() decorator. This decorator is responsible for providing the data which will allow the other providers to be injected as dependencies into the class. The dependency injection will help you in keeping the component classes efficient and lean. They will not perform any functionality like fetching the data from the server, performing the validation of the user input, or login to the console directly. There will be a delegation of such tasks to these services 

Differences between Angular and Angular Js: 

Let me give you a brief explanation of Angular and Angularjs before I explain about the differences between them. 

Angular: Angular is referred to as one of the open-source types of the framework that is created by Google which is specifically designed for developing web applications as per the client requirements. The developers in most of the organisations are making use of this Angular framework which is helping in creating, presenting and manipulating the data efficiently.The updated Angular version has got rich features when compared to the older version of Angular. There is one feature called CLI which is newly added and allows you to create the scaffolding for the Angular project that you are working on. 

Angular Js: Angular Js is also referred to as an open source front-end framework which is specifically used for designing single page web applications. AngularJs has become popular for advanced features when compared to Angular. It is also referred to as one of the expanding frameworks which is providing the different ways and options for the developers to develop the web applications. AngularJS has come up with the features where it allows the changes from the static HTML to the dynamic HTML along with some dynamic binding and the dependency injection which will help in eliminating the need for the code to be written again. There are different versions of Angular Js available and the latest version is 1.7.7. Most of them get confused and think that Angular and Angular Js are the same, but they are different. AngularJs can be used freely and allowed to perform the modifications or changes by anyone.

Let us discuss the differences between AngularJs and Angular based on some terminologies. 

Architecture: 

Angular Js: Angular Js provides its extensible support for the model view controller design. The view  is responsible for processing the information that is available in the model in order to generate the output when the user input is given. 

Angular: Angular consists of the components and directives. These are called building blocks of Angular. The components are referred to as the directive that are within the template. 

Mobile support: 

Angular Js: AngularJs does not provide support for the mobile browsers. 

Angular: Angular is flexible to provide it support for all the popular mobile browsers. 

Dependency injection: 

Angular Js: AngularJs does not have the concept of dependency injection. 

Angular: Angular makes use of the dependency injection concept which is used to represent the hierarchical dependency in the system. 

Expression Syntax: 

Angular Js: AngularJS uses ng-bind specifically to bind the data from the model to view and view to model. 

Angular: Angular makes use of the properties that will be enclosed in braces like [] or () to perform the binding between the model and view. 

Structure: 

Angular Js: The structure of AngularJs is less manageable when compared to Angular. 

Angular: Angular has a better structure when compared to Angular Js and it is also providing the flexibility to be users to create and maintain large applications easily. 

Angular Life cycle

A component in Angular Js will go through the eight phases in its life cycle. When the component is initialised it will create and present its root components. The design is performed and then it will produce the heirs. Once the components are loaded in the application development, it will be reviewing and checking if the data binding properties are getting changed or not. If the components are not used anymore, then they will be leading to the death phase in which the component will be decimated and expelled from the document object model. 

Components are important building blocks for the Angular version. It is essential for us to understand each and every component in it. The component will go through the life cycle and the stages of life cycles would be going from the initialisation to the destruction. There will be a need to write some additional code whenever these events take place. Let me give you a brief explanation about the life cycle of the component. 

Lifecycle Hook overview: 

The events that take place in the life of the component are called the lifecycle hook. Lifecycle hooks referred to the small functions that the developer will be calling during the specific point of the life of the component when they are working on the Angular application. It is also stated that the lifecycle hooks are referred to as a callback method that will be raised when a positive event takes place in the life cycle of the component. There are 8 kinds of hooks that are available in the life cycle of the component or a directive. They are: 

1. ngOnChanges(): 

This type of hook is used mostly in every component that has an input. 

The ngOnChanges() hook can be called whenever there is a change in the input value. 

The ngOnChanges() hook call the first time before the ngOnInit. 

2. ngOnInit(): 

The ngOnInit() hook is specifically used for initialising the data in the component. 

The ngOnInit() hook can be called only after the input values are set when the component initialization is done. 

The ngOnInit() hook can be added only to every component by default by making use of the Angular CLI. 

The ngOnInit() hook is allowed to be called only for once. 

3. ngDoCheck(): 

The  ngDoCheck() hook is called when the change detection runs. 

The  ngDoCheck() hook is used by a run through the view by Angular in order to make the detect or update the changes. 

4. ngAfterContentInit(): 

The ngAfterContentInit() hook will be called only once after the ngDoCheck(). 

The ngAfterContentInit()hook so we called after the first run of initializing the content. 

5.ngAfterContentChecked(): 

The ngAfterContentChecked() hook will be called after ngDoCheck(). 

The ngAfterContentChecked() hook will be waiting after the ngAfterContentInit() hook is on the first run through(). 

6. ngAfterViewInit(): 

The ngAfterViewInit() hook will be called after the Angular performs the initialization of the component and also the child component content. 

The ngAfterViewInit() hook will be called only once after the view is initialized. 

7. ngAfterViewChecked(): 

The ngAfterViewChecked() hook is called after the content is initialized and checked. It will include both the component and the child components. 

The ngAfterViewChecked() hook is first called after ngAfterViewInit() hook. 

The ngAfterViewChecked() hook will be called after every ngAfterContentChecked() call is completed. 

6. ngOnDestroy(): 

The  ngOnDestroy() hook is used to clean up the necessary code when the component is removed from the document object model. 

The ngOnDestroy() hook is used for  unsubscribing from things like services. 

The ngOnDestroy() hook will be called only once before the component is removed from the document object model.

Conclusion:

Angular is one of the best platforms that is being used for developing the applications. We see that there is an increase in the demand for the applications and development range is going high. There will be  higher opportunities available for the individuals who are looking for the job into the angular field. Hope the above information is helpful to you.As this is one of the robust frameworks, it will be used in most of the applications. I would recommend you to get trained and certified in Angular which food help you in attaining the best career.