What is the difference between RouterModule.forRoot() vs RouterModule.forChild()? Why is it important?

In Angular, RouterModule.forRoot() and RouterModule.forChild() are used to configure routes in the application. However, they serve different purposes and are used in different scenarios. Here is the difference:

1. RouterModule.forRoot(): This method is used in the application's root module, usually the AppModule. It takes a route configuration object and optionally a configuration object. It registers the RouterService to make it available throughout the application and also configures the router navigation for the root module. This method should be called only once in the application.

2. RouterModule.forChild(): This method is used in feature modules or any module other than the root module. This method also takes a route configuration object. The forChild() method doesn't register the RouterService again because the service is already available application-wide. This method allows the feature module to have its own local routing.

The importance of using these two methods correctly is essential:

• If we use forRoot() in feature modules, it will re-register the router service, which can lead to issues with the application routing.
• If we use forChild() in the root module, it will not register the router service, and the application won't be able to navigate between routes.

Therefore, always remember:

• Use RouterModule.forRoot() in your root module (AppModule).
• Use RouterModule.forChild() in your feature modules.