-Review, Research, and Discussion

- Name 3 real world use cases where you’d want to change the request with custom middleware

• Authentication (Auth middleware)
• Error Handling (Error Handing Middleware)
• Logging-in (Logging Middleware)

- True or false: The route handler is middleware?

• The route handler is middleware.

  - In what ways can a middleware function end the process and send data to the browser?

• Sending an error message by passing a string to next("string")
• without writing next().

  At what point in the request lifecycle can you “inject” middleware?

• Between in the middle of the request and the response .

  What can cause express to error with “Request headers sent twice, cannot start a second response”

• When a server tries to send several responses for one request.

  Vocabulary Terms

  Middleware :

• are functions that have access to the request object (req), the response object (res), and the next middleware function in the application’s request-response cycle.

  Request Object :

• Request is used to describe an request to a server.

  Response Object :

• The res object represents the HTTP response that an Express app sends when it gets an HTTP request.

  Application Middleware :

• a middleware that works on application level like authentication .

  Routing Middleware :

• a middleware that works on router level.

  Test Driven Development :

• is the act of first deciding what you want your program to do (the specifications), formulating a failing test, then writing the code to make that test pass.

  Behavioral Testing :

• focused on the behaviour of users rather than the technical functions of the software.

Classes

• Functions in JavaScript that create a template code that makes the code more readable and easy to use.
• Classes must be declared before used.

  Express Routing

• refers to how an application’s endpoints (URIs) respond to client requests.
• Routes is declered as follow: app.HTTP_method(Path, handler Function);
• To specify a middleware as the callback function we use : app.use() *************************

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