What is angular?
Angular is a JavaScript-based open-source front-end web framework mainly maintained by Google and by a community of individuals and corporations to address many of the challenges encountered in developing single-page applications.
Click here to setting up the local environment and work space.
<h2>Hero List</h2>
@Component({
<input [(ngModel)]="food.name">
<li *ngFor = "let food of foods”></li>
Angular is a JavaScript-based open-source front-end web framework mainly maintained by Google and by a community of individuals and corporations to address many of the challenges encountered in developing single-page applications.Click here to setting up the local environment and work space.
What is angular good for?
AngularJS is an open-source Front-end JavaScript framework. Its goal is to augment browser-based applications with Model–View–Controller (MVC) capability and reduce the amount of JavaScript needed to make web applications functional. These type of apps are also known as Single-Page Applications.
Why is angular faster?
The AOT compiler is much faster than it was in Angular 4 and it is also switched on by default. ... This makes Angular 5 faster in both development and production. Angular Universal Transfer API. Angular Universal provides server-side rendering of Angular applications which helps boost performance.
There are basically 8 building blocks of Angular 2. These are:
- Modules
- Components
- Templates
- Metadata
- Data binding
- Directives
- Services
- Dependency Injection
Let's go over each one of them one by one.
Angular-Architecture
Modules
Modules are blocks of code that do a certain type of task. A module exports some value in the main code, such as class. The first and the most common module that you will study is the one that exports Component Class.
app/app.component.ts (excerpt)
export class AppComponent { }
Here app.component is a module.
Libraries
Libraries' names start with the @angular prefix. Modules can be a library of other modules. Angular 2 itself has many modules that are libraries of others.
@angular/core is the most important library that contains most of the modules that we need.
Components
A component is basically a class that is used to show an element on the screen. The components have some properties and by using them we can manipulate how the element should look and behave on the screen. We can create a component, destroy, and update as the user moves in the application. Life Cycle hooks are the modules that we use for this purpose. Like ngOnInit()
app/app.component.ts (excerpt)
export class blogComponent { }
Here blogComponent is a component.
Templates
The view of the component is defined through templates. Templates are basically the HTML we use to show on our page.
app/hero-list.component.html
<h2>Hero List</h2>
<p><i>Pick a hero from the list</i></p>
<ul>
<li *ngFor="let food of foods" (click)="selectedFood(food)">
{{food.name}}
</li>
</ul>
<food-detail *ngIf="selectedFood" [food]="selectedHero"></food-detail>
This is a simple HTML file, but you may wonder: What are these elements?
<Is there an answer to this question?>
*ngFor,{{food.name}}, (click), [food], and <food-detail>?
Metadata
Metadata tells Angular how a class should be processed on the screen. For example:
@Component({
selector: 'food-list',
templateUrl: 'app/food-list.component.html',
directives: [FoodDetailComponent],
providers: [FoodService]
})
To tell Angular that we are using a component with certain metadata, we attach a decorator to it (“@”).
Here @Component will be identified as a component class.
Selector tells Angular to render the HTML that templateURL has at this tag <food-list></food-list>
Directives are other components that this Component will require to render and providers are the services required.
The template, metadata, and component together describe a view.
Data Binding
The main feature of any JavaScript framework is data binding. As Angular 1, Angular 2 also support data binding.
There are 4 ways of binding a data according to the direction to the DOM, from the DOM, or in both directions:
<input [(ngModel)]="food.name">
<li>{{food.name}}</li>
<food-detail [food]="selectedFood"></food-detail>
<li (click)="selectFood(food)"></li>
The {{hero.name}} interpolation display food.name value in li tag.
The [hero] property binding passes the selected food value from parent to child component.
The (click) event binding calls the selectedFood function when a user clicks on it.
Two-way data binding is an important fourth way that combines property and event binding by the ngModel directive.
Directive
Directive helps us to add behavior to the DOM elements. We can attach multiple directives to the DOM elements. In TypeScript we define decoratives by @decorative decorator.
There are 3 types of decorative:
- Directive-with-a-template
- Structural
- Attribute
A component is a directive-with-a-template:
Structural directives add, delete and replace DOM elements. For example:
<li *ngFor = "let food of foods”></li>
<food-detail *ngIf="selectedFood"></food-detail>
Attribute directives change the appearance of DOM elements. For example:
<input [(ngModel)]="hero.name">
Services
A service is a class containing any function, feature with a defined, and specific purpose. For example:
export class FoodService {
getfoodies(): Food[] {
return FOODIES;
}
}
Dependency Injections
Dependency injection allows one to inject a dependency as a service throughout the web application. To inject a dependency we do not create a service but we have a constructor to request the service. The framework then provides it. For example:
constructor(private service: HeroService) { }
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