Creating a Guard for Lazy-Loaded Modules in Angular

When building large applications in Angular, one feature that can significantly improve performance is lazy loading. This functionality enables the application to load modules only when they are needed. However, to ensure secure access to these lazy-loaded modules, you need to use a guard. According to the JSON formatted quiz, you can create a guard for lazy-loaded modules using a service with the CanLoad interface.

In Angular, the CanLoad interface governs whether a lazy-loaded module can be loaded or not, based on certain conditions. This method is especially useful for restricting access to modules based on user roles or ensuring conditions are met before a module is loaded.

Let's look at a practical example:

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

@Injectable({
  providedIn: 'root',
})
export class AuthGuard implements CanLoad {
  
  constructor(private authService: AuthService) {}

  canLoad(): boolean {
    return this.authService.isUserAuthenticated;
  }
}

In the above example, the CanLoad interface serves as a guard for the lazy-loaded module. The guard uses the AuthService to check if a user is authenticated. If the user is authenticated, the canLoad function will return true, and the corresponding module will be loaded. If not, the module won't be loaded.

Remember, the CanLoad guard only works for lazy-loaded modules in Angular. For eagerly-loaded modules, or routes that are loaded at the application start, you should use the CanActivate guard instead.

The use of CanLoad interface has an important advantage. It not only stops unauthorized users from accessing a route but it also prevents the Angular router from retrieving module files for unauthorized routes. This keeps the router lightweight and efficient.

To conclude, using a service with a CanLoad interface is the recommended and efficient way to create a guard for lazy-loaded modules in Angular. This method enables you to control module loading based on any conditions you need, optimizing both security and performance of your Angular applications.