Express foundations
Follow one Express request
Trace a request through Node, Express middleware, a route handler, and the final response.
9 minute lesson
Before choosing a tool or writing more code, make the requirement concrete. A request for /notes enters the app, crosses ordered middleware, matches one route, and ends when a response is sent or delegated.
Express is a thin request-routing and middleware layer on top of the Node HTTP server. The useful target is not encyclopedic coverage. Make one deliberate choice, observe its consequences, and know which requirement would make you revise it.
A common failure is to describe Express as a complete server that hides the Node request and response lifecycle. The happy path may still work, which makes the mistake easy to miss. draw the ordered request path and identify exactly which function ends or forwards it. Keep the first version small enough that every important input and output remains visible.
This supports the module goal: Start a small Express 5 application whose configuration and request path can be explained from the first byte. Capture the request, command, trace, screenshot, test result, or other evidence that proves the result.
Add three tiny middleware functions that log entry and exit, then predict and verify their order. Change one condition on purpose, predict the result, and compare the prediction with what actually happened.
Lesson completed