Loading CSS File on Runtime in an Application using Angular 17

Are you tired of dealing with static CSS files in your Angular application? Do you want to take your application to the next level by loading CSS files dynamically at runtime? Look no further! In this article, we’ll explore the world of dynamic CSS loading using Angular 17.

Why Load CSS Files Dynamically?

There are several reasons why loading CSS files dynamically can be beneficial for your application:

• Faster Development Cycle: With dynamic CSS loading, you can make changes to your CSS files without requiring a complete rebuild of your application.
• Improved Performance: By loading CSS files only when needed, you can reduce the overall payload size of your application, resulting in faster load times.
• Enhanced Customization: Dynamic CSS loading allows you to tailor your application’s appearance to specific user preferences or environmental conditions.

Step 1: Create a New Angular 17 Project

Before we dive into the world of dynamic CSS loading, let’s create a new Angular 17 project using the Angular CLI:

ng new angular-css-loading-example

Follow the prompts to complete the project setup, and then navigate into the project directory:

cd angular-css-loading-example

Step 2: Create a CSS File Loader Service

To load CSS files dynamically, we’ll create a service that will handle the loading process. Create a new file called `css-loader.service.ts` in the `src/app` directory:

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

@Injectable({
  providedIn: 'root'
})
export class CssLoaderService {

  private cssFiles: { [key: string]: string } = {};

  loadCssFile(cssFile: string): void {
    const linkElement = document.createElement('link');
    linkElement.rel = 'stylesheet';
    linkElement.href = cssFile;
    document.head.appendChild(linkElement);
  }

  removeCssFile(cssFile: string): void {
    const linkElements = document.querySelectorAll('link[rel="stylesheet"]');
    for (const linkElement of linkElements) {
      if (linkElement.href === cssFile) {
        document.head.removeChild(linkElement);
      }
    }
  }

}

This service provides two methods: `loadCssFile` and `removeCssFile`. The `loadCssFile` method creates a new `` element and appends it to the `` section of the document, while the `removeCssFile` method removes the corresponding `` element.

Step 3: Create a Component to Demonstrate Dynamic CSS Loading

Create a new component called `css-loader-example.component.ts` in the `src/app` directory:

import { Component, OnDestroy, OnInit } from '@angular/core';
import { CssLoaderService } from './css-loader.service';

@Component({
  selector: 'app-css-loader-example',
  template: `
    Load CSS File
    Remove CSS File
  `
})
export class CssLoaderExampleComponent implements OnInit, OnDestroy {

  constructor(private cssLoaderService: CssLoaderService) { }

  ngOnInit(): void {
    // Load a default CSS file
    this.cssLoaderService.loadCssFile('assets/css/default.css');
  }

  ngOnDestroy(): void {
    // Remove all CSS files
    this.cssLoaderService.removeCssFile('assets/css/default.css');
    this.cssLoaderService.removeCssFile('assets/css/custom.css');
  }

  loadCssFile(): void {
    this.cssLoaderService.loadCssFile('assets/css/custom.css');
  }

  removeCssFile(): void {
    this.cssLoaderService.removeCssFile('assets/css/custom.css');
  }

}

This component provides two buttons: one to load a custom CSS file and one to remove it. The `ngOnInit` lifecycle hook loads a default CSS file, while the `ngOnDestroy` lifecycle hook removes all loaded CSS files.

Step 4: Add the CSS Files

Create two CSS files: `default.css` and `custom.css` in the `src/assets/css` directory:

/* default.css */
body {
  background-color: #f2f2f2;
}

/* custom.css */
body {
  background-color: #ffffff;
}

The `default.css` file sets the background color of the body element to a light gray, while the `custom.css` file sets it to white.

Step 5: Render the Component

Finally, render the `CssLoaderExampleComponent` in the `app.component.html` file:

<app-css-loader-example></app-css-loader-example>

Result

Run the application using the following command:

ng serve

Open your browser and navigate to `http://localhost:4200`. You should see a page with two buttons. Click the “Load CSS File” button to load the custom CSS file, and click the “Remove CSS File” button to remove it. Observe how the background color of the body element changes dynamically.

Button Clicked	Background Color
Load CSS File	White (#ffffff)
Remove CSS File	Light Gray (#f2f2f2)

Conclusion

In this article, we’ve explored the world of dynamic CSS loading using Angular 17. We created a service to load and remove CSS files, a component to demonstrate the functionality, and added some CSS files to complete the picture. By following these steps, you can take your Angular application to the next level by loading CSS files dynamically at runtime.

Best Practices

When loading CSS files dynamically, keep the following best practices in mind:

1. Use a consistent naming convention: Use a consistent naming convention for your CSS files to avoid conflicts.
2. Load CSS files lazily: Load CSS files only when needed to reduce the overall payload size of your application.
3. Remove unused CSS files: Remove unused CSS files to avoid cluttering the `` section of your document.

By following these best practices and the steps outlined in this article, you’ll be well on your way to creating a dynamic and customizable Angular application.

Resources

For more information on Angular and dynamic CSS loading, check out the following resources:

• Angular Style Guide
• W3Schools CSS Examples

Happy coding!

Here are 5 Questions and Answers about “Loading CSS file on runtime in an application using Angular 17” in a creative voice and tone:

Frequently Asked Question

Get ready to dive into the world of Angular 17 and learn how to load CSS files on the fly!