This article divides deep into building websites with Node.js and Express.js. Express.js is an essential framework for creating robust and scalable web applications on top of Node.js, and today's focus will be on routing, middleware, template engines, and cookie sessions.
Concept Highlights:
- app.use(callback)
- app.use(path, callback)
- GET, POST, PUT, DELETE
- Express Middleware
- Call the Next Middleware in the Stack
- Using Express Router
- Cookie Session Management Middleware
- Template Variables
- EJS
1. app.use(callback)
The app.use(callback) method in Express.js is used to mount middleware functions. This middleware will run for every request made to your application, regardless of the HTTP method or URL.
e.g.) In this example, the middleware runs for every incoming request and logs a message to the console.
const express = require('express'); const app = express(); app.use((req, res, next) => { console.log('Middleware running for every request.'); next(); });
2. app.use(path, callback)
This method allows you to mount middleware at a specific route. The middleware will only run if the request matches the specified path.
e.g.) In this example, the middleware will only be triggered for routes that start with /users.
app.use('/users', (req, res, next) => { console.log('Middleware only for /users route.'); next(); });
3. GET, POST, PUT, DELETE
These methods allow you to handle specific HTTP methods (GET, POST, PUT, DELETE, etc.) at a specific route. This is where you define the behavior of your web application.
e.g.) Each method handles a different part of CRUD operations (Create, Read, Update, Delete) for user management.
app.get('/users', (req, ress) => { res.send('Fetching all users'); }); app.post('/users', (req, res) => { res.send('Creating a new user'); }); app.put('/users/:id', (req, res) => { res.send(`Updating user with ID: ${req.params.id}`); }); app.delete('/users/:id', (req, res) => { res.send('Deleting user with ID: ${req.params.id}`); });
4. Express Middleware
Middleware functions in Express.js have access to the request (req) and response (res) objects, and they can execute code, make modifications, or terminate the request-response cycle.
Key Features:
- Execute code: you can perform any logic or operations.
- Modify request/response: middleware can update headers, add data to req, or modify the res object.
- End request-response cycle: middleware can send data back to the client and end the cycle.
e.g.) In this example, middleware adds custom data to the request object and the route handler accesses it.
app.use((req, res, next) => { req.customData = 'Some custom data'; next(); }); app.get('/', (req, res) => { res.send(`Data from middleware: ${req.customData}`); });
5. Calling the Next Middleware
In the example above, I use next() to pass control to the next middleware or route handler. Without calling next(), the request would hang because the cycle wouldn't move forward.
e.g.) This ensures that each piece of middleware can pass control to the next in the chain.
const express = require('express'); const app = express(); app.use((req, res, next) => { console.log('Middleware running for every request.'); next(); });
6. Using Express Router
Express Router is a great tool for organizing routes in modular applications. It helps you break down your routes into smaller, manageable pieces.
e.g.) In this example, the router is mounted at /users, and requests to /users/profile will be handled by the router's route.
app.use('/users', (req, res, next) => { console.log('Middleware only for /users route.'); next(); });
7. Cookie Session Management Middleware
Handling sessions and cookies is crucial for managing user authentication and state. Express.js provides middleware to manage session data.
e.g.) Using express-session, I initialize a session and set session data, which can be accessed throughout the user's session.
app.get('/users', (req, ress) => { res.send('Fetching all users'); }); app.post('/users', (req, res) => { res.send('Creating a new user'); }); app.put('/users/:id', (req, res) => { res.send(`Updating user with ID: ${req.params.id}`); }); app.delete('/users/:id', (req, res) => { res.send('Deleting user with ID: ${req.params.id}`); });
8. Template Variables
When rendering views using template engines, you can pass variables to dynamically generate content. For example, in EJS, you can pass variables to your views for rendering.
e.g.) In this example, I pass the title and message variables to the EJS template.
app.use((req, res, next) => { req.customData = 'Some custom data'; next(); }); app.get('/', (req, res) => { res.send(`Data from middleware: ${req.customData}`); });
9. EJS (Embedded JavaScript)
EJS is a popular templating engine that allows you to write HTML and embed JavaScript directly within the HTML structure. It is simple but powerful and integrates well with Express.js for dynamic web pages.
e.g.) The syntax is used to inject JavaScript expressions into the HTML.
app.use((req, res, next) => { console.log('First middleware'); next(); }); app.use((req, res, next) => { console.log('Second middlware'); });
The above is the detailed content of Building a Website with Node.js and Express.js. For more information, please follow other related articles on the PHP Chinese website!

Yes, the engine core of JavaScript is written in C. 1) The C language provides efficient performance and underlying control, which is suitable for the development of JavaScript engine. 2) Taking the V8 engine as an example, its core is written in C, combining the efficiency and object-oriented characteristics of C. 3) The working principle of the JavaScript engine includes parsing, compiling and execution, and the C language plays a key role in these processes.

JavaScript is at the heart of modern websites because it enhances the interactivity and dynamicity of web pages. 1) It allows to change content without refreshing the page, 2) manipulate web pages through DOMAPI, 3) support complex interactive effects such as animation and drag-and-drop, 4) optimize performance and best practices to improve user experience.

C and JavaScript achieve interoperability through WebAssembly. 1) C code is compiled into WebAssembly module and introduced into JavaScript environment to enhance computing power. 2) In game development, C handles physics engines and graphics rendering, and JavaScript is responsible for game logic and user interface.

JavaScript is widely used in websites, mobile applications, desktop applications and server-side programming. 1) In website development, JavaScript operates DOM together with HTML and CSS to achieve dynamic effects and supports frameworks such as jQuery and React. 2) Through ReactNative and Ionic, JavaScript is used to develop cross-platform mobile applications. 3) The Electron framework enables JavaScript to build desktop applications. 4) Node.js allows JavaScript to run on the server side and supports high concurrent requests.

Python is more suitable for data science and automation, while JavaScript is more suitable for front-end and full-stack development. 1. Python performs well in data science and machine learning, using libraries such as NumPy and Pandas for data processing and modeling. 2. Python is concise and efficient in automation and scripting. 3. JavaScript is indispensable in front-end development and is used to build dynamic web pages and single-page applications. 4. JavaScript plays a role in back-end development through Node.js and supports full-stack development.

C and C play a vital role in the JavaScript engine, mainly used to implement interpreters and JIT compilers. 1) C is used to parse JavaScript source code and generate an abstract syntax tree. 2) C is responsible for generating and executing bytecode. 3) C implements the JIT compiler, optimizes and compiles hot-spot code at runtime, and significantly improves the execution efficiency of JavaScript.

JavaScript's application in the real world includes front-end and back-end development. 1) Display front-end applications by building a TODO list application, involving DOM operations and event processing. 2) Build RESTfulAPI through Node.js and Express to demonstrate back-end applications.

The main uses of JavaScript in web development include client interaction, form verification and asynchronous communication. 1) Dynamic content update and user interaction through DOM operations; 2) Client verification is carried out before the user submits data to improve the user experience; 3) Refreshless communication with the server is achieved through AJAX technology.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Linux new version
SublimeText3 Linux latest version

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.
