What are the built-in modules of nodejs?

Node.js is a very popular JavaScript running environment. It can not only run in the browser, but also run JavaScript on the server side. There are many built-in modules in Node.js that make Node.js a powerful server-side platform. In this article, we will explore some of the important features of Node.js built-in modules.

fs module

The fs module of Node.js is a module that interacts with the file system. It provides many functions such as reading files, writing files, creating folders, deleting folders, etc. We can use it to process files and directories, as well as check the status of files and directories.

For example, if you want to read the contents of a file, you can use the following code:

const fs = require('fs');

fs.readFile('filename.txt', 'utf8', (err, data) => {
  if (err) throw err;
  console.log(data);
});

Here, we use the readFile method to read filename. txtThe content of the file. The second parameter specifies the encoding format. If omitted, the read content will be binary data. After the file reading is completed, the callback function will be called and the contents of the file will be output.

http module

The http module of Node.js allows us to create an HTTP server that can listen and handle client requests. Using the http module, you can easily build a web server to handle HTTP requests and responses.

For example, we can create an HTTP server using the following code:

const http = require('http');

const server = http.createServer((req, res) => {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
});

server.listen(8080, () => {
  console.log('Server running at http://localhost:8080/');
});

In this example, we create an HTTP server and listen on port 8080. When the client requests, a "Hello World" string is returned as the response content.

path module

The path module of Node.js provides some useful functions for processing file paths. It can easily create and manipulate file paths.

For example, we can use the following code to merge paths:

const path = require('path');

const filePath = path.join('/usr', 'local', 'bin');
console.log(filePath);

In this example, we use the join method to merge the various parts of the path. The final output is '/usr/local/bin'.

os module

The os module of Node.js provides some functions for accessing operating system information. It can provide operating system information such as computer name, operating system type, operating system version, etc.

For example, we can use the following code to get the architecture type of the operating system:

const os = require('os');

console.log(os.arch());

In this example, we use the arch method to get the architecture type of the operating system, The output may be 'x64' or 'arm64', etc.

events module

The events module of Node.js is an event emitter in Node.js. Through it we can create and handle events.

For example, we can use the following code to handle the "message" event:

const EventEmitter = require('events');

class MyEmitter extends EventEmitter {}

const myEmitter = new MyEmitter();

myEmitter.on('message', (msg) => {
  console.log('Received message:', msg);
});

myEmitter.emit('message', 'Hello World!');

In this example, we created a MyEmitter class and bound a "message" to its instance Event handler function. When the event is triggered, the output prints out the received message.

The above is an introduction to some Node.js built-in modules. In addition to the above modules, Node.js has many other modules, such as Buffer module, crypto module, stream module, etc., which all provide many useful functions that can help us develop efficient and feature-rich applications in Node.js.

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