Express.js 5 migration guide

Express.js, a popular Node.js framework, has released version 5 which brings numerous updates aimed at enhancing efficiency and functionality, though it may introduce deprecation warnings and require careful migration from Express v4. Key improvements in Express 5 include changes to path route matching syntax, handling of rejected promises and middleware errors, and the reintroduction of the app.router object. The new version also maintains the port in the req.host object and changes the req.query object to a getter. Despite these updates, some features from Express 4, such as the app.del() function and certain request functions, have been deprecated. The tutorial guides users in upgrading from Express 4 to Express 5, demonstrating the process through a practical example of building a web application, while also highlighting the importance of testing and updating project dependencies.