Boosting Angular Application Performance: Tips and Best Practices 🚀

Saunak Surani
Widle Studio LLP
Published in
20 min readAug 12, 2023

Angular is a powerful and popular framework for building dynamic web applications. However, as applications grow in size and complexity, there can be performance bottlenecks that affect user experience. In this article, we will explore various techniques and best practices to improve the performance of Angular applications, ensuring they run smoothly and efficiently.

Angular Application Performance: A Comprehensive Guide to Boosting Speed and Efficiency 🚀

Table of Contents:

  1. Optimize Change Detection
    1.1. OnPush Change Detection Strategy
    1.2. Immutable Data Structures
    1.3. Using trackBy with ngFor
  2. Lazy Loading and Code Splitting
    2.1. Lazy Loading Modules
    2.2. Code Splitting with Dynamic Imports
  3. AOT Compilation
    3.1. Ahead-of-Time (AOT) vs. Just-in-Time (JIT)
    3.2. Configuring AOT Compilation
  4. Bundle Optimization
    4.1. Tree Shaking
    4.2. Minification and Uglification
    4.3. Source Maps
  5. Optimizing CSS
    5.1. Use SCSS and CSS Preprocessors
    5.2. Reduce CSS Selectors and Specificity
    5.3. Apply CSS Reset and Normalize
  6. Performance Profiling and Auditing
    6.1. Angular Performance Profiler
    6.2. Chrome DevTools and Lighthouse
  7. Virtual Scrolling and Infinite Loading
    7.1. Virtual Scrolling with CDK
    7.2. Implementing Infinite Loading
  8. Caching and Data Management
    8.1. Client-Side Caching with Service Workers
    8.2. Smart Data Loading with NgRx
  9. Optimizing Images and Assets
    9.1. Image Compression
    9.2. WebP Format for Supported Browsers
  10. PWA Features for Performance
    10.1. Offline Support with Service Workers
    10.2. Push Notifications
  11. Optimizing Network Requests
    11.1. HTTP Interceptors
    11.2. Minimize Requests and Payloads
  12. Managing Memory and Unsubscribing
    12.1. Memory Leaks and Subscription Management
    12.2. Unsubscribing in ngOnDestroy
  13. Performance Testing and Benchmarking
    13.1. Performance Testing Tools
    13.2. Setting Performance Benchmarks
  14. Server-Side Rendering (SSR)
    14.1. Angular Universal
    14.2. Pros and Cons of SSR
  15. Continuous Monitoring and Optimization
    15.1. Automated Performance Checks
    15.2. Performance Budgets
  16. Conclusion

1. Optimize Change Detection

Angular’s change detection mechanism is responsible for detecting changes in data and updating the view accordingly. However, it can become inefficient if not used optimally, resulting in unnecessary checks and updates.

1.1. OnPush Change Detection Strategy

The default change detection strategy in Angular is called “Default” or “CheckAlways.” It means that every time there is any change in the application, Angular triggers a change detection cycle for all components, regardless of whether they are affected by the change or not. This can lead to performance issues, especially in large applications.

To improve performance, you can use the “OnPush” change detection strategy for specific components. The “OnPush” strategy tells Angular to only run change detection for a component when its input properties change or when an event is triggered within the component.

To use the “OnPush” strategy, set the changeDetection property of the component to ChangeDetectionStrategy.OnPush:

import { Component, ChangeDetectionStrategy } from '@angular/core';

@Component({
selector: 'app-example-component',
templateUrl: './example.component.html',
changeDetection: ChangeDetectionStrategy.OnPush,
})
export class ExampleComponent {
// Component logic here
}

By using “OnPush,” you reduce unnecessary change detection cycles and improve the performance of the component.

1.2. Immutable Data Structures

Angular’s change detection works by comparing the current data with the previous data to determine if there are any changes. If you are using mutable data structures, such as arrays or objects, modifying their properties can result in change detection triggering, even if the actual data remains the same.

To mitigate this, consider using immutable data structures, where the data cannot be changed once created. Libraries like Immutable.js or Immer can help you work with immutable data in a more convenient way.

For example, using Immer, you can create immutable copies of your data while still being able to modify them in a readable and straightforward manner:

import { produce } from 'immer';

const originalData = { count: 0 };
const newData = produce(originalData, (draft) => {
draft.count += 1;
});
console.log(originalData.count); // Output: 0
console.log(newData.count); // Output: 1

1.3. Using trackBy with ngFor

When using *ngFor to iterate over a list of items, Angular needs a way to track changes to

the items and efficiently update the DOM. By default, Angular uses the index of the item in the array as the tracking mechanism. However, this can lead to performance issues, especially when items are added, removed, or re-ordered from the list.

To optimize *ngFor, use the trackBy function to provide a unique identifier for each item:

<app-item *ngFor="let item of items; trackBy: trackItemById"></app-item>

In the component, define the trackItemById function to return a unique identifier for each item:

import { Component } from '@angular/core';

@Component({
selector: 'app-example-component',
templateUrl: './example.component.html',
})
export class ExampleComponent {
items: Item[];
trackItemById(index: number, item: Item): number {
return item.id;
}
}

With trackBy, Angular can efficiently update the DOM when items change, significantly improving performance.

2. Lazy Loading and Code Splitting

Loading the entire application at once can result in a longer initial loading time, affecting the perceived performance of your application. Lazy loading and code splitting are techniques to load only the necessary parts of the application when they are needed, reducing the initial load time.

2.1. Lazy Loading Modules

Angular allows you to split your application into multiple modules and load them dynamically using lazy loading. With lazy loading, each module is loaded only when the user navigates to a specific route that requires that module.

To set up lazy loading, create a separate module for each feature or section of your application and use the loadChildren property in the routing configuration:

const routes: Routes = [
// Normal eager-loaded route
{ path: 'home', component: HomeComponent },
// Lazy-loaded route
{ path: 'lazy', loadChildren: () => import('./lazy/lazy.module').then(m => m.LazyModule) },
];

With lazy loading, the initial bundle size is reduced, and the user only loads the modules they actually use.

2.2. Code Splitting with Dynamic Imports

In addition to lazy loading modules, you can further optimize your application’s bundle size by using dynamic imports. Dynamic imports allow you to load parts of your application’s code on-demand, reducing the size of the initial bundle.

To use dynamic imports, utilize the dynamic import() function to load modules or components when needed:

@Component({
selector: 'app-example-component',
templateUrl: './example.component.html',
})
export class ExampleComponent {
async loadLazyComponent() {
const { LazyComponent } = await import('./lazy/lazy.component');
// Do something with the LazyComponent, e.g., render it dynamically
}
}

By using dynamic imports, you can delay the loading of non-essential code until it is required, leading to faster initial loading times.

3. AOT Compilation

Ahead-of-Time (AOT) compilation is an optimization technique that compiles Angular templates and components during the build process, rather than at runtime like Just-in-Time (JIT) compilation. AOT compilation offers several benefits, including faster loading times, smaller bundle sizes, and improved security.

3.1. Ahead-of-Time (AOT) vs. Just-in-Time (JIT)

With JIT compilation, the Angular templates are compiled and interpreted by the browser at runtime, which can lead to slower initial loading times. On the other hand, AOT compilation translates the templates and components into JavaScript during the build process, resulting in faster loading times and better runtime performance.

To enable AOT compilation, use the — aot flag when running the Angular CLI build command:

ng build --prod --aot

By enabling AOT compilation, you can improve the overall performance and load times of your Angular application.

3.2. Configuring AOT Compilation

When using AOT compilation, it’s essential to ensure that your application is compatible and free of any potential issues that may arise during the build process. Certain Angular features, such as dynamic template URLs or string-based CSS class bindings, are not compatible with AOT and need to be adjusted.

Angular provides a handy CLI tool called ngc, which can check your application’s compatibility with AOT compilation. Use the following command to run the ngc compiler:

ngc

Running ngc will check for any potential issues and provide guidance on how to resolve them.

4. Bundle Optimization

Optimizing your application’s bundles is crucial for improving the performance of your Angular application. By reducing the size of your bundles, you can achieve faster loading times and better overall performance.

4.1. Tree Shaking

Tree shaking is a process that eliminates unused code from your bundles during the build process. It ensures that only the code that is actually used in your application is included in the final bundle, reducing its size.

To enable tree shaking, make sure you are using ES6 modules in your code, as it allows the build tools to identify and eliminate unused code.

4.2. Minification and Uglification

Minification and uglification are techniques that reduce the size of your JavaScript and CSS files by removing unnecessary characters, such as whitespace and comments. Minification can significantly reduce the size

of your bundles and improve loading times.

The Angular CLI automatically performs minification and uglification when building the application for production:

ng build --prod

By including the — prod flag, the Angular CLI will apply minification and uglification to your bundles.

4.3. Source Maps

While minification and uglification are essential for reducing bundle size, they can make debugging more challenging, as the code becomes difficult to read. Source maps provide a mapping between the minified code and the original code, allowing you to debug and inspect your code in its original form.

Source maps are automatically generated by the Angular CLI when building the application for production:

ng build --prod

However, to ensure that source maps are included in the build, make sure the “sourceMap” option is set to true in your angular.json file:

{
"projects": {
"your-project-name": {
"architect": {
"build": {
"options": {
"sourceMap": true
}
}
}
}
}
}

5. Optimizing CSS

The performance of your Angular application is not just dependent on JavaScript; CSS also plays a significant role. Optimizing your CSS can lead to faster rendering times and improved user experience.

5.1. Use SCSS and CSS Preprocessors

Using a CSS preprocessor like SCSS allows you to organize your CSS code more efficiently and make it more maintainable. SCSS provides features like variables, mixins, and nested rules, which can help you write cleaner and more modular CSS code.

To use SCSS in your Angular application, you need to install the sass package:

npm install sass --save-dev

After installing the sass package, you can start using SCSS files (with a .scss extension) in your application.

5.2. Reduce CSS Selectors and Specificity

CSS selectors with high specificity can slow down rendering times, especially when the browser has to apply styles to multiple elements. Aim to keep your CSS selectors as simple as possible and avoid using overly specific rules.

Additionally, try to reduce the number of CSS selectors in your stylesheets. The more selectors you have, the more work the browser needs to do to apply the styles.

5.3. Apply CSS Reset and Normalize

Browsers apply default styles to HTML elements, which can lead to inconsistent styles across different browsers. To ensure a consistent starting point for your styles, consider using a CSS reset or normalize stylesheet.

A CSS reset sets all CSS properties to a consistent baseline, whereas normalize provides more nuanced and cross-browser consistent styles.

Include a CSS reset or normalize in your stylesheets to ensure a consistent starting point for your application:

/* Example CSS Reset */
html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed,
figure, figcaption, footer, header, hgroup,
menu, nav, output, ruby, section, summary,
time, mark, audio, video {
margin: 0;
padding: 0;
border: 0;
font-size: 100%;
font: inherit;
vertical-align: baseline;
}
/* More styles and selectors can be added as needed */

6. Performance Profiling and Auditing

Regularly profiling and auditing your Angular application’s performance can help identify potential bottlenecks and areas for improvement. Several tools and techniques can help you analyze your application’s performance.

6.1. Angular Performance Profiler

Angular comes with built-in performance profiling tools that can help you understand how your application performs. To access the Angular performance profiler, add ?profile=true to the URL of your application:

http://localhost:4200/?profile=true

This will enable the performance profiler, and you can use the developer tools to inspect the profiling results.

6.2. Chrome DevTools and Lighthouse

Chrome DevTools provide various performance-related features that can help you identify performance issues in your application. The Performance tab allows you to record and analyze performance metrics, such as load times, JavaScript execution, and rendering performance.

Additionally, you can use Lighthouse, an open-source tool from Google, to audit your application’s performance and get actionable recommendations for improvements. Lighthouse provides a comprehensive report on various performance aspects of your application, including performance, accessibility, SEO, and more.

7. Virtual Scrolling and Infinite Loading

If your application deals with large lists or datasets, virtual scrolling, and infinite loading can significantly improve performance by loading and rendering only the visible items.

7.1. Virtual Scrolling with CDK

The Angular Component Dev Kit (CDK) provides a virtual scrolling module that enables virtual scrolling for lists, tables, or other container elements. Virtual scrolling loads only the items that are currently visible on the screen, reducing the number of DOM elements and improving performance.

To use virtual scrolling, you need to install the @angular/cdk package:

npm install @angular/cdk --save

Next, import the ScrollingModule from the @angular/cdk/scrolling package and add it to your application’s module:

import { NgModule } from '@angular/core';
import { ScrollingModule } from '@angular/cdk/scrolling';

@NgModule({
imports: [ScrollingModule],
})
export class AppModule {}

Now you can use the cdk-virtual-scroll-viewport component to enable virtual scrolling for a list of items:

<cdk-virtual-scroll-viewport itemSize="50" class="example-viewport">
<div *cdkVirtualFor="let item of items" class="example-item">
{{ item }}
</div>
</cdk-virtual-scroll-viewport>

By using virtual scrolling, you can handle large datasets efficiently without affecting the application’s performance.

7.2. Implementing Infinite Loading

Infinite loading is a technique where new data is loaded as the user scrolls down the page, providing a seamless experience without the need for manual pagination or loading more data explicitly.

To implement infinite loading, you need to detect when the user scrolls to the bottom of the page and trigger the loading of additional data.

First, you need to handle the scroll event in your component:

import { Component, HostListener } from '@angular/core';

@Component({
selector: 'app-example-component',
templateUrl: './example.component.html',
})
export class ExampleComponent {
items: Item[] = [];
isLoading = false;
@HostListener('window:scroll', ['$event'])
onScroll(event: Event): void {
// Check if the user has scrolled to the bottom of the page
const isAtBottom = window.innerHeight + window.scrollY >= document.body.scrollHeight;
if (isAtBottom && !this.isLoading) {
this.loadMoreData();
}
}
loadMoreData(): void {
// Load more data here (e.g., from an API) and add it to the items array
// Set isLoading to true while loading and false when the data is loaded
}
}

In the example above, we use the HostListener decorator to listen for the scroll event on the window. When the user scrolls to the bottom of the page, the onScroll method is called, and we can then trigger the loading of more data.

By implementing infinite loading, you can provide a smoother user experience and prevent performance issues associated with loading large datasets all at once.

8. Caching and Data Management

Caching and efficient data management are essential for improving the performance of your Angular application, especially when dealing with data from APIs or external sources.

8.1. Client-Side Caching with Service Workers

Service workers are scripts that run in the background and allow your application to cache data and assets. By using service workers, you can store certain resources locally on the user’s device, reducing the need to fetch them from the network every time the user visits your application.

To implement client-side caching with service workers, you need to create a service worker script and register it in your application.

First, create a service worker file (e.g., sw.js) and add the caching logic:

const CACHE_NAME = 'my-app-cache-v1';
const urlsToCache = ['/index.html', '/styles.css', '/app.js'];

self.addEventListener('install', (event) => {
event.waitUntil(
caches.open(CACHE_NAME).then((cache) => {
return cache.addAll(urlsToCache);
})
);
});
self.addEventListener('fetch', (event) => {
event.respondWith(
caches.match(event.request).then((response) => {
// Cache hit - return the cached response
if (response) {
return response;
}
// If the request is not cached, fetch it from the network
return fetch(event.request);
})
);
});

In the above example, we cache the index.html, styles.css, and app.js files when the service worker is installed. Then, when a fetch event occurs (i.e., when the application tries to fetch a resource), the service worker intercepts the request and checks if it exists in the cache. If it does, the cached response is returned; otherwise, the request is fetched from the network.

Next, register the service worker in your application’s main.ts file:

if ('serviceWorker' in navigator) {
navigator.serviceWorker.register('/sw.js')
.then(() => console.log('Service Worker registered successfully.'))
.catch((error) => console.error('Error registering Service Worker:', error));
}

By implementing client-side caching with service workers, you can significantly improve the performance of your application, especially for users with slower or unreliable network connections.

8.2. Smart Data Loading with NgRx

NgRx is a state management library for Angular applications, which allows you to manage your application’s data and state in a centralized store. By using NgRx, you can implement smart data loading strategies, such as lazy loading or on-demand data fetching, to improve performance.

To use NgRx, you need to install the @ngrx/store package:

npm install @ngrx/store --save

Next, set up your store, actions, reducers, and effects according to your application’s data management requirements.

For example, you can use NgRx to implement lazy loading of data when a user navigates to a specific route:

import { Component } from '@angular/core';
import { Store } from '@ngrx/store';
import { loadItems } from './store/actions/items.actions';

@Component({
selector: 'app-example-component',
templateUrl: './example.component.html',
})
export class ExampleComponent {
constructor(private store: Store) {}
ngOnInit(): void {
this.store.dispatch(loadItems());
}
}

In this example, the loadItems action is dispatched when the component is initialized, triggering the loading of the required data from the store or an external API.

By utilizing NgRx and smart data loading techniques, you can ensure that your application loads and manages data efficiently, leading to better performance and a smoother user experience.

9. Optimizing Images and Assets

Images and other assets can significantly contribute to the overall size of your application, impacting loading times. Optimizing your images and assets is essential for improving performance.

9.1. Image Compression

Compressing images can significantly reduce their file size without sacrificing too much quality. You can use various image compression tools and techniques to optimize your images before including them in your application.

For example, you can use online image compression tools like TinyPNG or ImageOptim to reduce the size of your images.

Additionally, the Angular CLI provides built-in support for image optimization during the build process. By including the — prod flag, the CLI will automatically optimize images in your application:

ng build --prod

9.2. WebP Format for Supported Browsers

WebP is a modern image format developed by Google that offers superior compression and quality compared to traditional image formats like JPEG and PNG. It is supported by most modern browsers, including Chrome, Firefox, and Opera.

To serve WebP images to supported browsers, you can use the picture element with the source element:

<picture>
<source srcset="path/to/image.webp" type="image/webp">
<img src="path/to/image.jpg" alt="Image">
</picture>

By using WebP images, you can further reduce the size of your application’s images and improve loading times for users on supported browsers.

10. PWA Features for Performance

Progressive Web Apps (PWAs) are web applications that leverage modern web technologies to provide a more app-like experience to users. PWAs can significantly impact the performance of your application, especially in terms of offline support and background synchronization.

10.1. Offline Support with Service Workers

As mentioned earlier, service workers enable client-side caching and can provide offline support for your application. By caching critical resources, such as HTML, CSS, and JavaScript files, you can ensure that users can still access your application even when they are offline.

Additionally, you can use the Cache Storage API to cache dynamic data from APIs, allowing users to access certain parts of your application even when they have no internet connection.

10.2. Push Notifications

Push notifications are an essential feature of PWAs that can help re-engage users and provide timely updates. By implementing push notifications, you can notify users about new content, updates, or other relevant information, even when they are not actively using your application.

To enable push notifications, you need to implement a server-side push notification service and handle the subscription and notification process in your Angular application.

By incorporating PWA features into your application, you can enhance its performance, user experience, and engagement.

11. Optimizing Network Requests

Network requests, such as API calls and data fetching, can impact the performance of your Angular application. Optimizing how you make and handle network requests can lead to a more responsive application.

11.1. HTTP Interceptors

Angular provides HTTP interceptors, which allow you to intercept and modify HTTP requests and responses. Interceptors are useful for various purposes, such as adding authentication tokens to requests, handling errors, or caching responses.

For example, you can use an interceptor to add an authentication token to each outgoing request:

import { Injectable } from '@angular/core';
import { HttpInterceptor, HttpRequest, HttpHandler, HttpEvent } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
// Add the authentication token to the request
const authToken = 'your-auth-token';
const authRequest = request.clone({ setHeaders: { Authorization: `Bearer ${authToken}` } });
return next.handle(authRequest);
}
}

To use the interceptor, you need to provide it in your application’s module:

import { NgModule } from '@angular/core';
import { HTTP_INTERCEPTORS } from '@angular/common/http';
import { AuthInterceptor } from './auth.interceptor';

@NgModule({
providers: [
{ provide: HTTP_INTERCEPTORS, useClass: AuthInterceptor, multi: true },
],
})
export class AppModule { }

11.2. Minimize Requests and Payloads

Reducing the number of network requests and optimizing the payloads can significantly improve the performance of your Angular application.

For example, consider combining multiple API requests into a single request using batch endpoints or GraphQL queries. This can reduce the number of round trips to the server and improve overall loading times.

Additionally, aim to minimize the size of the data being sent between the server and the client. Avoid sending unnecessary data in API responses and consider using compression techniques, such as Gzip, to reduce payload size.

12. Managing Memory and Unsubscribing

Properly managing memory and subscriptions is crucial for maintaining the performance and stability of your Angular application.

12.1. Memory Leaks and Subscription Management

Improperly managed subscriptions can lead to memory leaks in your application. When a component is destroyed, it’s essential to unsubscribe from all subscriptions to prevent memory leaks and unnecessary processing.

You can use the unsubscribe() method to unsubscribe from subscriptions in the OnDestroy lifecycle hook:

import { Component, OnDestroy } from '@angular/core';
import { Subscription } from 'rxjs';

@Component({
selector: 'app-example-component',
templateUrl: './example.component.html',
})
export class ExampleComponent implements OnDestroy {
private dataSubscription: Subscription;
constructor(private dataService: DataService) {
this.dataSubscription = this.dataService.getData().subscribe((data) => {
// Process the data
});
}
ngOnDestroy(): void {
this.dataSubscription.unsubscribe();
}
}

By unsubscribing from subscriptions, you ensure that your application releases resources when they are no longer needed, leading to better performance and preventing memory-related issues.

12.2. Unsubscribing in ngOnDestroy

It’s crucial to always unsubscribe from subscriptions in the ngOnDestroy lifecycle hook. However, manually managing subscriptions can be error-prone and time-consuming, especially in complex applications.

To simplify the subscription management process, consider using the takeUntil operator from RxJS along with a subject to track the component's lifecycle:

import { Component, OnDestroy } from '@angular/core';
import { Subject } from 'rxjs';
import { takeUntil } from 'rxjs/operators';

@Component({
selector: 'app-example-component',
templateUrl: './example.component.html',
})
export class ExampleComponent implements OnDestroy {
private unsubscribe$ = new Subject<void>();
constructor(private dataService: DataService) {
this.dataService.getData()
.pipe(takeUntil(this.unsubscribe$))
.subscribe((data) => {
// Process the data
});
}
ngOnDestroy(): void {
this.unsubscribe$.next();
this.unsubscribe$.complete();
}
}

With the takeUntil operator, the subscription is automatically unsubscribed when the unsubscribe$ subject emits a value, which happens when the component is destroyed in the ngOnDestroy lifecycle hook.

By using takeUntil and the unsubscribe$ subject, you can simplify the management of subscriptions and prevent memory leaks in your Angular application.

13. Performance Testing and Benchmarking

Regularly testing and benchmarking the performance of your Angular application can help you identify areas that need improvement and track the impact of optimizations over time.

13.1. Performance Testing Tools

Several tools and frameworks can assist you in performance testing and benchmarking:

  • Lighthouse: As mentioned earlier, Lighthouse is a tool that audits your application’s performance and provides recommendations for improvement. It can be run as a browser extension or as a CLI tool.
  • WebPageTest: WebPageTest allows you to test your application’s performance from various locations and provides detailed metrics and analysis of your application’s load times.
  • Google Chrome DevTools: Chrome DevTools offers various performance-related features, such as the Performance tab for recording and analyzing performance metrics.
  • Angular Performance Profiler: The built-in Angular performance profiler can be used to inspect and measure the performance of your Angular application.

13.2. Setting Performance Benchmarks

Once you have selected a performance testing tool, you can establish performance benchmarks for your application. Benchmarking allows you to set performance targets and monitor whether your application meets those targets.

For example, you can set benchmarks for the following metrics:

  • Load time: The time it takes for your application to load and become interactive.
  • Time to First Byte (TTFB): The time it takes for the server to respond with the first byte of data.
  • Time to Interactive (TTI): The time it takes for your application to become fully interactive.
  • Largest Contentful Paint (LCP): The time it takes for the largest element on the page to become visible.
  • Cumulative Layout Shift (CLS): A measure of the visual stability of the page, especially for elements that move during loading.

By regularly testing your application against these benchmarks, you can identify performance regressions and assess the impact of optimizations.

14. Server-Side Rendering (SSR)

Server-Side Rendering (SSR) is a technique that renders your Angular application on the server before sending it to the client’s browser. SSR can improve the initial load time and provide better SEO and social media sharing capabilities.

14.1. Angular Universal

Angular Universal is a framework for server-side rendering in Angular applications. It allows you to render your application on the server, providing a pre-rendered HTML response to the client’s browser. Subsequent interactions in the client’s browser will be handled by the standard Angular SPA.

To add server-side rendering to your Angular application, you need to install the @angular/platform-server package:

npm install @angular/platform-server --save

Next, you need to set up your application for SSR by creating a server module and a server main file:

// server.ts (server entry point)
import 'zone.js/node';
import 'reflect-metadata';
import { enableProdMode } from '@angular/core';
import { ngExpressEngine } from '@nguniversal/express-engine';
import { provideModuleMap } from '@nguniversal/module-map-ngfactory-loader';
import * as express from 'express';
import { join } from 'path';

// Import the main server bundle generated by the Angular CLI
import { AppServerModuleNgFactory, LAZY_MODULE_MAP } from './dist/server/main';
enableProdMode();
const app = express();
app.engine('html', ngExpressEngine({
bootstrap: AppServerModuleNgFactory,
providers: [provideModuleMap(LAZY_MODULE_MAP)],
}));
app.set('view engine', 'html');
app.set('views', join(__dirname, 'dist/browser'));
app.get('*.*', express.static(join(__dirname, 'dist/browser')));
app.get('*', (req, res) => {
res.render('index', { req });
});
app.listen(4000, () => {
console.log('Server listening on port 4000');
});

In the server.ts file, we import the main server bundle generated by the Angular CLI and use ngExpressEngine to render the application on the server.

Once your server is set up, you can build your Angular application for server-side rendering using the Angular CLI:

ng build --prod --app=your-app-name

The --app=your-app-name flag specifies the app you want to build for SSR if you have multiple applications in your Angular project.

After building your application, start the server using the node command:

node server.js

With Angular Universal and SSR, your application’s initial load time will improve, enhancing the user experience and search engine discoverability.

14.2. Pros and Cons of SSR

Server-Side Rendering has several advantages and some trade-offs:

Pros:

  • Faster initial load time: Pre-rendering your application on the server reduces the time it takes for the initial page to load and become interactive.
  • Improved SEO: Search engines can more easily crawl and index the pre-rendered content, improving SEO and search engine discoverability.
  • Better social media sharing: When sharing links on social media platforms, the pre-rendered content will be visible, providing a better user experience.

Cons:

  • Increased server load: Server-Side Rendering can increase the server load, especially for applications with high traffic. Proper server infrastructure is needed to handle the increased demand.
  • Complexity: Adding SSR to an existing Angular application can be complex and require adjustments to components, services, and state management.
  • Longer time to interactive: While SSR improves the initial load time, it does not eliminate the need to load and execute JavaScript. As a result, the time to interactive may be longer compared to fully client-side rendered applications.

Whether to implement SSR depends on your application’s requirements and performance goals. For content-heavy websites or applications that prioritize SEO, SSR can be a valuable addition to enhance performance and user experience.

15. Continuous Monitoring and Optimization

Optimizing Angular application performance is not a one-time task. To maintain high-performance levels, continuous monitoring and optimization are essential.

15.1. Automated Performance Checks

Integrate automated performance checks into your development and deployment processes. You can use tools like Lighthouse, WebPageTest, or custom performance testing scripts to regularly test your application’s performance.

Set up automated scripts or CI/CD pipelines to run performance checks after every deployment. This way, you can quickly identify any performance regressions and take action to resolve them.

15.2. Performance Budgets

Set performance budgets for your application. Performance budgets define the maximum allowable limits for metrics such as bundle size, loading times, and other performance indicators.

By setting performance budgets, you can prevent performance regressions and ensure that your application stays within acceptable performance levels.

16. Conclusion

Improving the performance of your Angular application requires a holistic approach, considering various factors that can impact performance. By optimizing change detection, lazy loading modules, and using AOT compilation, you can reduce the initial load time and bundle size.

Optimizing CSS, leveraging virtual scrolling and infinite loading, and smart data management can improve rendering times and data handling. Additionally, implementing server-side rendering, using PWAs, and managing subscriptions can further enhance performance and user experience.

Continuous monitoring and benchmarking help you identify areas for improvement and ensure that your application meets its performance goals. With careful attention to performance, you can create a fast, responsive, and efficient Angular application that delights your users and delivers a seamless experience.

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Saunak Surani
Widle Studio LLP

Passionate about technology, design, startups, and personal development. Bringing ideas to life at https://widle.studio