Detailed explanation of how to install and configure Express in nodejs

Node.js is a lightweight JavaScript platform that can run on the server side to quickly build high-performance, scalable applications. Express is one of the Node.js application frameworks and is widely used in the Node.js world. It provides a set of simple and easy-to-use interfaces to help developers quickly build server-side applications. This article will show you how to install and configure Express in Node.js.

1. Node.js installation

Before installing Express, you need to install Node.js first. Node.js can download the latest version of the installation package from the official website http://nodejs.org/. During the installation process, you only need to follow the default prompts to complete the installation of Node.js.

2. Install Express

Express can be installed through the command line tool. Open a terminal or command line window and enter the following command:

$ npm install express

or

$ npm install -g express

The first command will install Express under the project path, and the second command will install Express under the global path. Installing Express globally may require administrator privileges.

After the installation is complete, to integrate Express into the Node.js project, you need to create a new folder in the project directory and name it "node_modules". Copy the Express package inside the "node_modules" folder into this folder.

Next, add the following code in the project's "app.js" file to enable Express:

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

3. Express basic configuration

Configuring Express needs to be in the app Call some functions on the object and pass some parameters. The following is the basic setup method for configuring Express.

1. Set routing

Routing refers to the URL mapping of server-side applications, usually consisting of HTTP methods and URL paths. Express allows routing to be set through functions such as "app.get" and "app.post".
For example, the following is the code for setting routing:

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

In the above code, the "app.get" function means that when the HTTP request method is "GET" and the URL path is "/", the server will Respond to the "Hello World!" string.

2. Set up middleware

Middleware refers to the logical processing function executed before processing requests and responses. Express allows setting middleware through the "app.use" function.
For example, the following is the code to set up middleware:

app.use(express.static('public'));

In the above code, the "express.static" function means to serve static files to files in the specified directory. All static file requests will be automatically responded to.

3. Set up the template engine

The template engine allows the server to dynamically generate HTML content to provide a good user experience to the client. Express allows setting the template engine through the "app.set" function.
For example, the following is the code to set the template engine:

app.set('view engine', 'ejs');

In the above code, "view engine" represents the name of the view engine, and "ejs" represents the use of the EJS template engine.

4. Express operation

After completing the basic configuration of Express, you can use the following code to start the server:

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

In the above code, the "app.listen" function means Listen on port 3000 to receive client requests. After the server is started, enter "http://localhost:3000/" in the browser to access it.

Summary

Through this article, you have learned how to install and configure Express in Node.js, and how to build a basic Express server. Express is rich in features and highly customizable, and is worthy of your in-depth understanding and exploration.

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