Event Type Typescript Angular with Code Examples
Angular is a popular framework for building web applications. It provides a wide range of features that enable developers to create complex web applications with ease. One of the essential features that Angular provides is event handling. Events play a crucial role in web applications, and Angular provides a robust event handling system that developers can use to create interactive and responsive applications.
In this article, we will discuss event types in Angular and how to handle them using TypeScript. We'll also look at some code examples to help you understand how to work with events in Angular.
Types of Events in Angular
Angular provides several types of events that can occur during the lifecycle of a component. These events can be classified as follows:
- DOM Events
DOM events are browser-specific events that occur when a user interacts with the web page. These events include click, mouseover, keyup, and more. Angular provides several directives, such as (click), (mouseover), and (keyup), that can be used to handle DOM events.
For example, let's say we have a button that we want to click to trigger an event. We can add the (click) directive to the button element and bind it to a function that will handle the event.
<button (click)="handleEvent()">Click Me</button>
In the above code, we've added the (click) directive to the button element and bound it to the handleEvent() function. This function will be called whenever the button is clicked.
- Component Events
Component events are custom events that are emitted by components. These events can be used to communicate between components or pass data to other components. To create a component event, we must first define an event type using the EventEmitter class.
import { EventEmitter } from '@angular/core';
export class MyComponent {
myEvent = new EventEmitter<string>();
}
In the above code, we've defined a component called MyComponent with an EventEmitter that emits a string value. We can then use this event to emit values from the component and handle them in other components.
To emit an event, we can call the emit() method on the event emitter instance.
this.myEvent.emit('event data');
In the above code, we've emitted an event with a string value called 'event data'. We can then handle this event in another component by subscribing to it.
@Component({
selector: 'app-child-component',
template: `
<div>{{ eventData }}</div>
`
})
export class ChildComponent {
eventData: string;
@Input() myEvent: EventEmitter<string>;
ngOnInit() {
this.myEvent.subscribe(data => {
this.eventData = data;
});
}
}
In the above code, we have a child component called ChildComponent that subscribes to the myEvent event emitted by MyComponent. We've used the @Input() decorator to receive the event emitter instance from the parent component, and we've handled the emitted values in the ngOnInit() lifecycle hook.
- Router Events
Router events are events that occur when the Angular router navigates to a new route. These events are emitted by the Router class and can be used to perform certain actions when the route changes.
import { Router, NavigationStart } from '@angular/router';
export class AppComponent {
constructor(private router: Router) {
router.events.subscribe(event => {
if (event instanceof NavigationStart) {
// Do something when navigation starts
}
});
}
}
In the above code, we've subscribed to the router.events observable to listen to router events. We've used the NavigationStart event to perform some action when navigation starts.
Conclusion
Events play a critical role in web applications as they allow developers to create interactive and responsive applications. Angular provides a robust event handling system that developers can use to handle various types of events. In this article, we've discussed the three types of events in Angular (DOM events, component events, and router events) and how to handle them using TypeScript. We hope this article has helped you understand how to work with events in Angular and provided you with some code examples to help you get started.
here's some additional information about the previous topics mentioned in the article.
DOM Events
DOM events are the browser-specific events that occur when a user interacts with the web page. Angular provides several directives that can be used to handle DOM events, such as (click), (mouseover), and (keyup).
When using directives to handle DOM events, we can pass the event object to the function that will handle the event. For example:
<button (click)="handleClick($event)">Click Me</button>
In the above code, we've passed the $event object to the handleClick() function. This object contains information about the event, such as the target element, the type of event, and more.
Component Events
Component events are custom events that can be emitted by components and used to communicate between components or pass data to other components.
To emit an event, we first define an event type using the EventEmitter class, as shown in the previous example. We then call the emit() method on the event emitter instance to emit the event.
To handle the emitted event, we can subscribe to the event in another component using the EventEmitter instance. We can also pass data with the emitted event by passing it as an argument to the emit() method.
Router Events
Router events occur when the Angular router navigates to a new route. Angular provides several router events, such as NavigationStart, NavigationEnd, NavigationCancel, and NavigationError, that can be used to perform certain actions when the route changes.
To listen to router events, we can subscribe to the router.events observable, which emits all router events. We can then check the type of the emitted event and perform the necessary actions.
For example, we can use the NavigationStart event to show a loader while the page is loading:
import { Router, NavigationStart } from '@angular/router';
export class AppComponent {
isLoading = false;
constructor(private router: Router) {
router.events.subscribe(event => {
if (event instanceof NavigationStart) {
this.isLoading = true;
} else {
this.isLoading = false;
}
});
}
}
In the above code, we've subscribed to the router.events observable and checked if the emitted event is an instance of NavigationStart. If it is, we set the isLoading flag to true, which shows a loader in the template. When the navigation is complete, we set the isLoading flag to false, which hides the loader.
Conclusion
In conclusion, event handling is an essential feature in Angular that enables developers to create interactive and responsive applications. Angular provides several types of events, such as DOM events, component events, and router events, that can be used to handle various events in the lifecycle of a component. It's essential to understand how to handle these events using TypeScript, and we hope this article has provided you with a better understanding of event handling in Angular.
Popular questions
- What are the three types of events in Angular?
- The three types of events in Angular are DOM events, component events, and router events.
- How can we handle DOM events in Angular?
- We can handle DOM events in Angular using directives such as (click), (mouseover), and (keyup). We can also pass the event object to the function that will handle the event by using the $event object.
- What is a component event in Angular?
- A component event in Angular is a custom event that can be emitted by components. We can define an event type using the EventEmitter class and emit the event using the emit() method. We can then handle the emitted event in other components by subscribing to it using the EventEmitter instance.
- What is a router event in Angular?
- A router event in Angular is an event that occurs when the Angular router navigates to a new route. Angular provides several router events, such as NavigationStart, NavigationEnd, NavigationCancel, and NavigationError, that can be used to perform certain actions when the route changes.
- How can we use router events in Angular?
- To use router events in Angular, we can subscribe to the router.events observable, which emits all router events. We can then check the type of the emitted event and perform the necessary actions. For example, we can use the NavigationStart event to show a loader while the page is loading.
Tag
TechEvent
