Summary
Highlights
This section introduces Express.js as a backend framework for JavaScript. It covers initial setup steps including installing Node.js, initializing a new npm project (npm init -y), installing Express (npm i express), and setting up Nodemon for automatic server restarts during development (npm i -D nodemon). A `dev:start` script is configured in `package.json` to run `nodemon server.js`.
The video demonstrates how to create a basic Express server using `require('express')` and `app.listen()`. It explains how to define routes for different HTTP methods like GET, POST, PUT, and DELETE using `app.get()`. The function takes a path and a callback with `req` (request) and `res` (response) objects. Examples are given for sending responses using `res.send()`, `res.sendStatus()`, `res.status().send()`, and `res.json()`.
This part covers sending files for download using `res.download()` and rendering HTML files for dynamic content using `res.render()`. It introduces the concept of view engines and specifically demonstrates setting up EJS (Embedded JavaScript) as the view engine by installing `ejs` and configuring `app.set('view engine', 'ejs')`. It also shows how to pass data from the server to EJS templates and access it within the templates, including handling undefined variables with `locals`.
To maintain code organization, the tutorial explains how to use Express Routers. By creating separate files (e.g., `routes/users.js`), routes related to specific resources (like users) can be grouped. A router is created with `express.Router()` and then mounted onto the main application using `app.use('/users', userRouter)`. This allows for nested routing and avoids repeating base paths.
This section delves into creating dynamic routes using parameters, such as `/users/:id`. It demonstrates how to access these parameters through `req.params`. A crucial point is highlighted: static routes (e.g., `/users/new`) must be defined before dynamic routes (e.g., `/users/:id`) to ensure correct matching. The video also introduces `router.route()` for chaining multiple HTTP methods (GET, PUT, DELETE) on the same dynamic path for cleaner code.
The concept of middleware in Express is explained as functions that run between a request and its response. The `router.param()` function is introduced as a powerful middleware that executes whenever a specific parameter (e.g., 'id') is encountered in a route. This allows for pre-processing logic, such as fetching user data based on the ID, and storing it in the `req` object for subsequent middleware or route handlers. The importance of calling `next()` in middleware is emphasized to proceed to the next handler.
The video distinguishes between global middleware (applied to all routes using `app.use()`) and route-specific middleware (passed directly to route handlers). It demonstrates how to create a simple logger middleware. Furthermore, it covers serving static files (HTML, CSS, JavaScript) using the built-in `express.static()` middleware, typically by creating a 'public' directory.
This segment focuses on parsing incoming request bodies. It shows how to use `express.urlencoded({ extended: true })` middleware to process data from HTML forms (e.g., `req.body.firstName`). An example of creating a new user and redirecting is provided, including handling invalid input by re-rendering the form with previous data. Finally, it explains how to parse JSON data using `express.json()` and how to access query parameters from the URL (e.g., `?name=Kyle`) using `req.query.name`.