Angular Bundle Optimization Challenge: Lazy Loading and Chunking

Angular applications can sometimes suffer from large initial bundle sizes, leading to slow load times and a poor user experience. This challenge focuses on implementing bundle optimization techniques – specifically lazy loading of modules and strategic chunking – to reduce the initial bundle size and improve application performance. You'll be tasked with refactoring an existing Angular application to leverage these techniques.

Problem Description

You are given a basic Angular application with a main module and several feature modules. The current application loads all feature modules eagerly during the initial application load, resulting in a large initial bundle. Your task is to refactor the application to implement lazy loading for the feature modules, splitting them into separate chunks that are loaded on demand. This will significantly reduce the initial bundle size and improve the application's startup time.

What needs to be achieved:

• Implement lazy loading for at least three of the existing feature modules.
• Ensure that the lazy-loaded modules are only loaded when their corresponding routes are accessed.
• Maintain the functionality of the application after refactoring.
• Demonstrate a reduction in the initial bundle size compared to the original application (though precise measurement isn't required for this challenge, the intent is clear).

Key Requirements:

• Use Angular's routing module to define lazy-loaded routes.
• Structure the feature modules in a way that supports lazy loading (i.e., each module should have its own entry point).
• The application should continue to function correctly after the refactoring.
• The code should be well-structured, readable, and maintainable.

Expected Behavior:

• When the application starts, only the main module should be loaded initially.
• When a user navigates to a route associated with a lazy-loaded module, that module should be loaded asynchronously.
• Subsequent navigations to the same lazy-loaded module should utilize the cached chunk, avoiding redundant downloads.
• All existing application functionality should remain intact.

Edge Cases to Consider:

• Handling errors during module loading. (While error handling isn't explicitly required, consider how it might be implemented in a production environment).
• Circular dependencies between modules (ensure your lazy loading configuration doesn't introduce them).
• The impact of lazy loading on application startup time (aim for a noticeable improvement).

Examples

Example 1:

Assume we have a feature module called ProductsModule and a route /products.

Input: Original application loading all modules eagerly.
Output: Application where `ProductsModule` is loaded only when the user navigates to `/products`.
Explanation: The route configuration for `/products` is updated to lazy load `ProductsModule`.  The module's entry point is specified in the route configuration.

Example 2:

Assume we have three feature modules: ProductsModule, OrdersModule, and CustomersModule.

Input: Application loading all modules eagerly.
Output: Application where `ProductsModule`, `OrdersModule`, and `CustomersModule` are lazy-loaded when navigating to `/products`, `/orders`, and `/customers` respectively.
Explanation: Each module's route configuration is updated to lazy load the corresponding module.

Constraints

• Module Count: You must lazy load at least three feature modules.
• Input Format: The application will be provided with a pre-existing Angular project structure. You are expected to modify the routing configuration and module structure.
• Performance: While precise measurement isn't required, the goal is to demonstrably reduce the initial bundle size. Avoid unnecessary complexity that would hinder performance.
• Angular Version: Assume Angular version 16 or later.

Notes

• Consider using Angular's RouterModule.forChild() method when defining lazy-loaded routes within feature modules.
• The entry point for a lazy-loaded module is typically a file named module.ts within the module's directory.
• Focus on the core concepts of lazy loading and chunking. Advanced optimization techniques (e.g., code splitting based on component usage) are beyond the scope of this challenge.
• Think about how the lazy-loaded modules are structured and how their entry points are defined. This is crucial for Angular to correctly load them asynchronously.