Skip to main content

Angular 17 Feature: deferred loading @defer

Using @defer in Angular 17 to implement lazy loading.

Angular 17 introduced a new @defer block that lets you lazy-load content based on specific conditions or events.

Lazy loading is a technique that enables web apps to load resources (such as scripts) only when they are needed.

Using @defer with a declarative trigger condition

Deferred blocks support the following declarative trigger types:

1.      on interaction

2.      on hover

3.      on idle

4.      on timer

5.      on viewport

Let's create an example for all of these!

@defer on interaction

Angular renders the on interaction block when the user interacts with its @placeholder block. An interaction can be a click, focus, or input event, like keypress:

@defer (on interaction) {

  <span>Clicked - on interaction </span>

}

@placeholder {

  <span>Placeholder - on interaction (click on it!) </span>

}

@error {

    <span>Error</span>

}

@loading(minimum 2s) {

    <span class="red">Loading...</span>

}

 

@defer on hover

Angular renders the on hover block when the user hovers over its @placeholder block:

@defer (on hover) {

  <span>Hovered - on hover </span>

}

@placeholder {

  <span>Placeholder - on hover (hover it!)</span>

}

@error {

    <span>Error</span>

}

@loading(minimum 2s) {

    <span class="red">Loading...</span>

}

 

@defer on idle

Angular renders the on idle block when the browser reaches an idle state after the page has been loaded:

@defer (on idle) {

  <span>Browser has reached an idle state</span>

}

@placeholder {

  <span>Placeholder - on idle </span>

}

@error {

    <span>Error</span>

}

@loading(minimum 2s) {

    <span class="red">Loading...</span>

}

 

@defer on timer

The on timer block is rendered after the specified time has elapsed:

@defer (on timer(4s)) {

  <span>Visible after 4s</span>

}

@placeholder {

  <span>Placeholder – wait to 4s </span>

}

@error {

    <span>Error</span>

}

@loading(minimum 2s) {

    <span class="red">Loading...</span>

}

 

@defer on viewport

Angular renders the on viewport block when the placeholder enters the browser's viewport:

@defer (on viewport) {

  <app-user-list />

}

@placeholder {

  <span>Placeholder – on viewport</span>

}

@error {

    <span>Error</span>

}

@loading(minimum 2s) {

    <span class="red">Loading...</span>

}

 

For more detailed examples, see the YouTube video Link: - 

By Anil Singh | Rating of this article (*****)

Popular posts from this blog

39 Best Object Oriented JavaScript Interview Questions and Answers

Most Popular 37 Key Questions for JavaScript Interviews. What is Object in JavaScript? What is the Prototype object in JavaScript and how it is used? What is "this"? What is its value? Explain why "self" is needed instead of "this". What is a Closure and why are they so useful to us? Explain how to write class methods vs. instance methods. Can you explain the difference between == and ===? Can you explain the difference between call and apply? Explain why Asynchronous code is important in JavaScript? Can you please tell me a story about JavaScript performance problems? Tell me your JavaScript Naming Convention? How do you define a class and its constructor? What is Hoisted in JavaScript? What is function overloadin

List of Countries, Nationalities and their Code In Excel File

Download JSON file for this List - Click on JSON file    Countries List, Nationalities and Code Excel ID Country Country Code Nationality Person 1 UNITED KINGDOM GB British a Briton 2 ARGENTINA AR Argentinian an Argentinian 3 AUSTRALIA AU Australian an Australian 4 BAHAMAS BS Bahamian a Bahamian 5 BELGIUM BE Belgian a Belgian 6 BRAZIL BR Brazilian a Brazilian 7 CANADA CA Canadian a Canadian 8 CHINA CN Chinese a Chinese 9 COLOMBIA CO Colombian a Colombian 10 CUBA CU Cuban a Cuban 11 DOMINICAN REPUBLIC DO Dominican a Dominican 12 ECUADOR EC Ecuadorean an Ecuadorean 13 EL SALVADOR

25 Best Vue.js 2 Interview Questions and Answers

What Is Vue.js? The Vue.js is a progressive JavaScript framework and used to building the interactive user interfaces and also it’s focused on the view layer only (front end). The Vue.js is easy to integrate with other libraries and others existing projects. Vue.js is very popular for Single Page Applications developments. The Vue.js is lighter, smaller in size and so faster. It also supports the MVVM ( Model-View-ViewModel ) pattern. The Vue.js is supporting to multiple Components and libraries like - ü   Tables and data grids ü   Notifications ü   Loader ü   Calendar ü   Display time, date and age ü   Progress Bar ü   Tooltip ü   Overlay ü   Icons ü   Menu ü   Charts ü   Map ü   Pdf viewer ü   And so on The Vue.js was developed by “ Evan You ”, an Ex Google software engineer. The latest version is Vue.js 2. The Vue.js 2 is very similar to Angular because Evan You was inspired by Angular and the Vue.js 2 components looks like -

nullinjectorerror no provider for httpclient angular 17

In Angular 17 where the standalone true option is set by default, the app.config.ts file is generated in src/app/ and provideHttpClient(). We can be added to the list of providers in app.config.ts Step 1:   To provide HttpClient in a standalone app we could do this in the app.config.ts file, app.config.ts: import { ApplicationConfig } from '@angular/core'; import { provideRouter } from '@angular/router'; import { routes } from './app.routes'; import { provideClientHydration } from '@angular/platform-browser'; //This (provideHttpClient) will help us to resolve the issue  import {provideHttpClient} from '@angular/common/http'; export const appConfig: ApplicationConfig = {   providers: [ provideRouter(routes),  provideClientHydration(), provideHttpClient ()      ] }; The appConfig const is used in the main.ts file, see the code, main.ts : import { bootstrapApplication } from '@angular/platform-browser'; import { appConfig } from '

React | Encryption and Decryption Data/Text using CryptoJs

To encrypt and decrypt data, simply use encrypt () and decrypt () function from an instance of crypto-js. Node.js (Install) Requirements: 1.       Node.js 2.       npm (Node.js package manager) 3.       npm install crypto-js npm   install   crypto - js Usage - Step 1 - Import var   CryptoJS  =  require ( "crypto-js" ); Step 2 - Encrypt    // Encrypt    var   ciphertext  =  CryptoJS . AES . encrypt ( JSON . stringify ( data ),  'my-secret-key@123' ). toString (); Step 3 -Decrypt    // Decrypt    var   bytes  =  CryptoJS . AES . decrypt ( ciphertext ,  'my-secret-key@123' );    var   decryptedData  =  JSON . parse ( bytes . toString ( CryptoJS . enc . Utf8 )); As an Example,   import   React   from   'react' ; import   './App.css' ; //Including all libraries, for access to extra methods. var   CryptoJS  =  require ( "crypto-js" ); function   App () {    var   data