Being able to intercept HTTP requests is crucial in a real world application. Whether it is for error handling and logging or for injecting authentication tokens. While in Angular version 2 it intercepting HTTP requests was totally possible, implementing it wasn't that trivial and intuitive. Starting from Angular version 4.3.1 there is a new, way more simpler approach of implementing HTTP interceptors. In this lesson we're going to explore how.
You say in the video that you need to return the event from the .do operator. But this is not necessary. As can be seen in the plunker.