What are interceptors in Angular?

What are interceptors in Angular?

In Angular, interceptors are a powerful tool for intercepting HTTP requests and responses before they are sent to or received from the server. Interceptors are implemented as services that can be registered with the Angular dependency injection system and added to the HTTP pipeline.

Interceptors can be used for a variety of purposes, such as:

• Adding authentication headers to outgoing requests.
• Modifying or logging request data before it is sent.
• Catching errors and handling them in a centralized location.
• Modifying or transforming the response data before it is returned to the calling code.

To create an interceptor in Angular, you need to implement the HttpInterceptor interface, which has two methods:

1. Intercept: This method is called for each HTTP request and response. It takes two arguments, the HttpRequest and a HttpHandler, which represents the next interceptor in the pipeline. You can modify the request or response as needed, and then call the handle method on the HttpHandler to pass the request/response to the next interceptor in the pipeline.
2. Constructor: This method is used to inject any services that the interceptor needs.

Once you have created an interceptor, you can register it with the HttpClientModule by adding it to the provider's array in the NgModule metadata. Interceptors are executed in the order in which they are added to the provider's array, so be careful about the order in which you add them if you have multiple interceptors.

Overall, interceptors provide a flexible way to add common functionality to your HTTP requests and responses without having to modify each request or response individually.