Express Routing

• Event Driven System: when a get event happens on the server, check the route and run the function associated with that route

  app.get('/thing', (req,res) => {})
  

• The Request Object can take Parameters (:params) and Query Strings (?key=value)

• The Response Object is responsible for sending data back to the browser
  • Can send Headers with Cookies and Status Codes

Express Middleware

• Middleware can be divided into two categores:

  • Application Middleware includes error handling, bringing in other routes, applying defaults, JSON/Body/Form Parsing

  • Route Middleware deals with specific information for a route, such as are you logged in? Is it your first time on this route? What is your IP?

CRUD Operations with REST and Express

REST Method	CRUD Operation	Express Method Route	Function
POST	CREATE	app.post(‘/resource’)	Create a New Record
GET	READ	app.get(‘/resource’)	Retrieve 1+ Records
PUT	UPDATE	app.put(‘/resource/:id’)	Replace Record with an updated version
DESTROY	DELETE	app.get(‘/resource/:id’)	Remove a Record

Server Testing

• Best practice is to export your server as a module in a library and then use ‘supertest’ to run tests through the server without actually having to start the server for testing. This limits the variables involved in the test

• Similarly, ‘superagent’ can be wrapped in a module for testing so that the API is not actually called during server tests

Test Pyramid

• Units: Server Internal Functions
• Integration: How it connects to other services
• Acceptance

Express.js Fundamentals - 6 - Middleware Explained

• middleware: Any number of functions that are invoked by the Espress.js routing layer before your final request handler is made

  • All middleware functions carry an optional ‘next’ parameter, which is needed when passing along the request to the next function in the chain

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