Angular Components Overview & Examples

Angular is a popular JavaScript framework used to develop web applications. One of the key features of Angular is its ability to create reusable building blocks for web applications. These building blocks are called components. In this article, we’ll take a closer look at Angular components, their characteristics, and their practical use.

What are Angular Components?

Angular components are like the building blocks for creating web applications. Components in Angular are responsible for handling user interface elements and responding to user interactions. In simple terms, components represent a specific view with specific functionality. You can think of them as widgets or modules that contain HTML, CSS, and JavaScript code. Components are also reusable. Once you create a component, you can use it multiple times throughout your application.

Creating an Angular Component

To create a new Angular component, you can use the Angular CLI (Command Line Interface), which provides a simple command to generate a new component. Here’s an example:

“`
ng generate component my-component
“`

This command generates a new component called “my-component,” which includes the HTML, CSS, and TypeScript files required for the component. The generated files are created in the “src/app” directory.

Components use a specific file structure for organizing their code. The HTML, CSS, and TypeScript files for a component are stored in a single folder with the same name as the component. For example, the files for “my-component” are stored in a folder called “my-component.”

The HTML template for the component can be found in a file called “my-component.component.html.” The CSS styles for the component can be found in a file called “my-component.component.css.” And the TypeScript code for the component can be found in a file called “my-component.component.ts.”

Using an Angular Component

Once you’ve created an Angular component, you can use it in your application by importing it into other components or modules. Here’s an example:

“`
import { Component } from ‘@angular/core’;

@Component({
selector: ‘app-root’,
template: `

My App

`
})
export class AppComponent {}
“`

In this example, we’ve imported the “my-component” component and included it in the template for the “app-root” component. When the “app-root” component is rendered, it will include the “my-component” component.

Angular Component Lifecycle

Angular components have a specific lifecycle, which includes several stages. These stages are as follows:

1. ngOnChanges() – This event is triggered when the component’s input values change.
2. ngOnInit() – This event is triggered when the component is initialized.
3. ngDoCheck() – This event is triggered when the component’s data is checked for changes.
4. ngAfterContentInit() – This event is triggered when the component’s content has been initialized.
5. ngAfterContentChecked() – This event is triggered when the component’s content has been checked for changes.
6. ngAfterViewInit() – This event is triggered when the component’s view has been initialized.
7. ngAfterViewChecked() – This event is triggered when the component’s view has been checked for changes.
8. ngOnDestroy() – This event is triggered when the component is destroyed.

These events can be used to perform specific actions during the component’s lifecycle. For example, you can use the “ngOnInit()” event to perform initializations for your component.

Angular Component Example – Todo List

Let’s take a look at a simple example of an Angular component in action. We’ll build a “Todo List” application that allows users to add and remove items from a list. Here’s the HTML code for the application:

“`

“`

This code defines the structure of our “Todo List” application, including a form for adding new items to the list and a list of items already added.

Next, we’ll create an Angular component to handle the logic for our application. Here’s the TypeScript code for our component:

“`
import { Component } from ‘@angular/core’;

@Component({
selector: ‘app-todo-list’,
templateUrl: ‘./todo-list.component.html’,
styleUrls: [‘./todo-list.component.css’]
})
export class TodoListComponent {
newTodo: string = ”;
todos: Todo[] = [];

addTodo(): void {
if (this.newTodo.trim().length === 0) {
return;
}

this.todos.push({
text: this.newTodo.trim(),
completed: false
});

this.newTodo = ”;
}

remove(todo: Todo): void {
const index = this.todos.indexOf(todo);
this.todos.splice(index, 1);
}
}

interface Todo {
text: string;
completed: boolean;
}
“`

This code defines our “TodoListComponent” component and includes the logic for adding and removing todo items. The “addTodo()” function is used to add a new todo item to the list, and the “remove()” function is used to remove an item from the list.

Finally, we’ll include our “TodoListComponent” in our application by updating the “app.component.ts” file as follows:

“`
import { Component } from ‘@angular/core’;

@Component({
selector: ‘app-root’,
templateUrl: ‘./app.component.html’,
styleUrls: [‘./app.component.css’]
})
export class AppComponent {}
“`

We’ll also update the “app.component.html” file to include our “TodoListComponent”:

“`

“`

Now, when we run our application, we’ll see our “Todo List” application in action.

FAQs

1. What are the benefits of using Angular components?
Angular components offer numerous benefits, including code reuse, improved application modularity, and increased development efficiency.

2. Do I have to use the Angular CLI to create components?
No, you can manually create components, but using the Angular CLI provides a faster and more efficient way to create components.

3. What happens if I delete a component?
If you delete a component, any references to that component in your application will be removed, and the component’s files will be deleted from your project.

4. Can I use other libraries with Angular components?
Yes, you can use other libraries with Angular components, as long as they are compatible with Angular.

Overall, Angular components offer a powerful and flexible way to develop web applications. By breaking down your application into reusable components, you can improve your application’s modularity and increase development efficiency. With Angular components, the possibilities are endless.