How to Use the Async Pipe in Angular?
Last Updated :
15 Oct, 2024
The AsyncPipe in Angular is a powerful and convenient tool used to handle asynchronous data streams such as observables and promises directly in the component template. It automatically subscribes to observables, renders their values, and updates the view when new data is emitted.
This removes the need for manual subscriptions or managing observables inside the component code, making it easier to work with reactive programming in Angular applications.
Steps for Using the Async Pipe in Angular
Step 1: Install Angular CLI (if not installed)
First, make sure you have the Angular CLI installed. If not, install it by running:
npm install -g @angular/cli
Step 2: Create a New Angular Project (if needed)
You can create a new Angular project using the Angular CLI:
ng new async-pipe-demo
cd async-pipe-demo
Step 3: Install RxJS (Reactive Extensions)
Angular comes with RxJS installed by default, so you don’t need to install it separately in most cases. However, if it's missing, you can install it with:
npm install rxjs
Project Structure:
Project StructureUpdated Dependencies:
"dependencies": {
"@angular/animations": "^17.3.0",
"@angular/common": "^17.3.0",
"@angular/compiler": "^17.3.0",
"@angular/core": "^17.3.0",
"@angular/forms": "^17.3.0",
"@angular/platform-browser": "^17.3.0",
"@angular/platform-browser-dynamic": "^17.3.0",
"@angular/platform-server": "^17.3.0",
"@angular/router": "^17.3.0",
"@angular/ssr": "^17.3.7",
"express": "^4.18.2",
"rxjs": "~7.8.0",
"tslib": "^2.3.0",
"zone.js": "~0.14.3"
}
Approach of using Async Pipe in Angular
- DataService: Provides an observable using RxJS of() that simulates fetching data asynchronously.
- AsyncPipeExampleComponent: Fetches the data and assigns it to the data$ observable.
- AsyncPipe (| async): Subscribes to the observable in the template and handles the value automatically, updating the UI when the observable emits data
Step 4: Add the code
In the (app.component.ts), you can define the observable or promise that will fetch data, for example, fetching mock data with Observable:
JavaScript
// src/app/app.component.ts
import { CommonModule } from '@angular/common';
import { Component, OnInit } from '@angular/core';
import { Observable, of } from 'rxjs';
@Component({
selector: 'app-root',
standalone:true,
templateUrl: './app.component.html',
imports: [CommonModule],
})
export class AppComponent implements OnInit {
data$: Observable<string[]> | undefined;
constructor() { }
ngOnInit(): void {
// Simulating an async operation with an Observable
this.data$ = this.getData();
}
// Function to simulate fetching data asynchronously
getData(): Observable<string[]> {
const data = ['Angular', 'Async Pipe', 'RxJS', 'Observable'];
return of(data); // 'of' creates an Observable that emits the array
}
}
JavaScript
// main.ts
import { bootstrapApplication } from '@angular/platform-browser';
import { AppComponent } from './app/app.component';
bootstrapApplication(AppComponent)
.catch(err => console.error(err));
Step 5: Add code in "app.component.html" file
Use AsyncPipe in the Template In the component template (app.component.html), use the AsyncPipe to display the data without manually subscribing to the observable:
HTML
<h1>Async Pipe Demo</h1>
<!-- Using AsyncPipe to display observable data in the template -->
<ul>
<li *ngFor="let item of data$ | async">{{ item }}</li>
</ul>
Step 6: Run the Application
Finally, run your Angular application to see the AsyncPipe in action:
ng serve
Output: Navigate to http://localhost:4200/ in your browser to view the result.
Output
Similar Reads
How To Use OnChanges In Angular?
Angular is a powerful framework for building dynamic web applications, and one of its core features is the ability to manage and react to changes in component data. One of the key lifecycle hooks in Angular for responding to changes in input properties is the OnChanges lifecycle hook. This hook is h
3 min read
How To Use @Injectable Decorator In Angular?
In Angular, the @Injectable decorator is used to mark a class as available for dependency injection. This allows Angular to create and manage instances of this class and inject it into other components, services, or other classes.In this article, we will see how to use the @Injectable decorator in a
3 min read
AngularJS | How to use ng-idle?
The ng-idle is used to decrease the burden, bandwidth, and workload of an app, website, program, or software. With the help of ng-idle log out the session of inactive users so that our precious data & the workload is getting preserved or to even taunt them to participate more actively. The ng-id
3 min read
How to access the value of a Promise in AngularJS ?
AngularJS is one of the JS frameworks that consists of promises that are used to handle asynchronous tasks. In some scenarios, we need to handle the promise values by accessing them in the application. So, this can be done using the .then() method and also by using the callbacks in AngularJS. In thi
4 min read
How To Use HttpClient in Angular?
In Angular, the HttpClient module is used to make HTTP requests to backend services. It simplifies communication with APIs, allowing developers to interact with RESTful services, send and receive data, and handle responses effectively. This article will guide you through setting up HttpClient, makin
6 min read
How to Use Lodash in Angular Applications?
Lodash is an open source library that helps in performing operations on various data structures like arrays, or objects, in a seamless and efficient way. When used with javascript frameworks, like angular, it can ease the life of developers while writing functions to manipulate arrays or objects. In
2 min read
HTTP Interceptor use-cases in Angular
In Angular, HTTP interceptors are a powerful feature that allows you to intercept and modify HTTP requests and responses at a centralized location. They act as middleware, sitting between the applicationâs HTTP client (typically the built-in HttpClient module) and the server.In this article, we will
6 min read
How to Get Page Load Time in Angular?
In web development, performance is the most important thing. Users expect fast and responsive web applications and even minor delays can impact user experience and satisfaction. Monitoring page load time is important for identifying performance bottlenecks and optimizing the user experience. In this
5 min read
How to create a custom pipe in AngularJS ?
In this article, we will learn how to generate custom pipe other than using built-in pipe in Angular & also explore its implementation. The Pipe is a function that is used to modify the data before rendering it to the user. Some of the pre-built pipes are date, uppercase, lowercase, currency, de
6 min read
How do you register custom pipes in Angular 17?
Angular provides a powerful feature called pipes, which allows you to transform data before displaying it in your component's template. While Angular comes with a set of built-in pipes, you can also create your own custom pipes to suit your specific requirements. In this article, we will explore how
3 min read