Angular

Angular is a JavaScript framework for building web applications that is developed and maintained by Google and is based on the Model-View-Controller (MVC) architecture pattern. It allows developers to build dynamic and highly-responsive web applications.

One of the key features of Angular is the use of components. A component is a self-contained piece of code that defines a view and the logic behind it. Each component has its own template, which defines the HTML layout, and a class, which defines the logic and data. This structure makes it easy to build and maintain large and complex web applications by separating the code into smaller, reusable components.

Another important feature is the use of two-way data binding, which automatically updates the view and the model when changes are made to either. This eliminates the need to manually update the view, which can save time and effort.

Angular also includes a powerful set of directives, special attributes that can be added to HTML elements to add functionality to the view. Directives can be used to add logic to the view, such as showing or hiding elements based on conditions or looping through collections of data. Additionally, it has a built-in dependency injection (DI) system, which makes it easy to manage dependencies between components and allows for easier testing and maintenance.

The framework also provides a powerful set of tools for building and deploying web applications. The Angular CLI is a command-line tool that can be used to create a new project and run it, and the Angular Compiler can be used to optimize and deploy the application to a production environment. It also has a robust routing system that allows you to navigate between different views in your application, and a built-in form validation system that allows you to validate user input in your forms.

Furthermore, Angular has a built-in service worker that provides offline support and caching for your application, and a built-in change detection system that helps to keep the view in sync with the data.

Finally, the framework has a large and active community that provides a wealth of resources and support for developers. There are many tutorials, articles, and sample code available to help you get started, as well as many third-party libraries and frameworks that can be used to add additional functionality to your application. Overall, Angular is a robust and feature-rich JavaScript framework that offers a lot of functionality out of the box.

Example

Here is an example of a simple “Hello World” Angular application:

Lets start with app component:

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  template: `<h1>Hello World!</h1>`
})
export class AppComponent { }

This code defines a component called “AppComponent” and uses the @Component decorator to define the component’s metadata. The selector property tells Angular to use the component when it finds the <app-root> tag in the HTML. The template property defines the HTML template for the component, which in this case is just a single heading that says “Hello World!”

You also need to import the component in the app.module.ts file

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { AppComponent } from './app.component';

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

Typical project structure:

helloword-app/
├── e2e/
├── node_modules/
├── src/
│   ├── app/
│   │   ├── app.component.ts
│   │   ├── app.module.ts
│   │   └── ...
│   ├── assets/
│   ├── environments/
│   ├── index.html
│   ├── main.ts
│   ├── polyfills.ts
│   ├── styles.css
│   ├── test.ts
│   ├── tsconfig.app.json
│   ├── tsconfig.spec.json
│   └── ...
├── package.json
├── package-lock.json
├── tsconfig.json
├── tslint.json
└── ...
  • The e2e/ directory contains end-to-end tests for the application.
  • The node_modules/ directory contains the npm packages that the application depends on.
  • The src/ directory contains the source code for the application.
    • The app/ directory contains the code for the application’s components, services, and other features.
    • The app.component.ts file contains the code for the AppComponent which we have discussed before.
    • The app.module.ts file contains the code for the AppModule which is the root module of the application.
    • The assets/ directory contains assets such as images and fonts.
    • The environments/ directory contains configuration files for different environments.
    • The index.html file is the application’s main HTML file.
    • The main.ts file is the application’s main entry point.
    • The polyfills.ts file contains polyfills for older browsers.
    • The styles.css file contains global styles for the application.
    • The test.ts file is the entry point for the application’s unit tests.
    • The tsconfig.app.json and tsconfig.spec.json files contain TypeScript configuration for the application and its tests, respectively.
  • The package.json file contains metadata about the application and its dependencies.
  • The package-lock.json file contains a detailed list of the application’s dependencies and their versions.
  • The tsconfig.json file contains TypeScript configuration for the entire application.
  • The tslint.json file contains linting rules for the application.