How to use the Express framework to build web applications

With the continuous development of Web technology, front-end development is becoming more and more important. Many people are keen to explore new technologies, among which Node.js has become a very popular technology. Node.js is a JavaScript runtime environment based on the Chrome browser V8 engine for developing high-performance, scalable web applications. Node.js aims to provide a lightweight and efficient solution to facilitate the development and deployment of applications on different platforms.

In Node.js, there are many ways to form pages. The most common one is to use web frameworks such as Express, Koa, Hapi, etc. These frameworks enable the creation of web applications quickly while providing many useful features and middleware. Here's how to use the Express framework to build web applications.

First, you need to install Express through the Node.js package manager (npm):

npm install express

Next, create a file named app.js in the project and write the following code:

const express = require('express');
const app = express();

app.get('/', function(req, res){
  res.send('Hello World!');
});

app.listen(3000, function(){
  console.log('App listening on port 3000!');
});

In the above code, we introduced the Express framework and created an Express instance. app.get()The method is used to match HTTP GET requests. When the user accesses the root path, a Hello World string will be returned. app.listen() method starts the application and listens to port 3000.

Save and run the file:

node app.js

Visit http://localhost:3000 in the browser, you can see the Hello World string. This is the basic process of creating a web application using the Express framework. Of course, in actual development, more processing logic and routing configuration are usually required.

The Express framework provides many useful functions and middleware, such as static file serving, template engine, parameter parsing, session management, etc. The following is an example of using static file service:

const express = require('express');
const path = require('path');
const app = express();

app.use(express.static(path.join(__dirname, 'public')));

app.get('/', function(req, res){
  res.sendFile(path.join(__dirname, 'index.html'));
});

app.listen(3000, function(){
  console.log('App listening on port 3000!');
});

Use express.static() method to provide static file service, path.join() method is used to Get the absolute path. app.get()The method returns the index.html file. This is a basic static file serving example. In actual development, you can also use a template engine to dynamically generate HTML pages.

In short, Node.js is a very powerful tool for creating high-performance, scalable web applications. Using the Express framework can simplify the web development process and improve development efficiency. Hope this article is helpful to you.

The above is the detailed content of How to use the Express framework to build web applications. For more information, please follow other related articles on the PHP Chinese website!