Let's talk about some commonly used built-in modules of node and their functions

Node.js is an open source running environment based on the Chrome V8 JavaScript engine, which allows JavaScript to run on the server side. Node.js is lightweight, efficient, and cross-platform, so it is very popular in web development, application development, data processing and other fields.

In actual development, we often need to interact with external interfaces, such as obtaining data, sending requests, etc. So, does Node.js itself have its own interface?

The answer is yes. Node.js provides many built-in modules that can be used to interact with external interfaces. Let's introduce some commonly used built-in modules and their functions one by one.

http

In Node.js, http is a built-in module used to create HTTP servers and clients. Through the http module, we can easily create an HTTP server that can handle HTTP requests and responses and provide interface functions to the outside world. For example, we can return different data based on different URL paths.

The following is a simple example:

const http = require('http');

const server = http.createServer((req, res) => {
  if (req.url === '/') {
    res.end('Hello, world!');
  } else if (req.url === '/about') {
    res.end('About us');
  } else {
    res.end('Not found');
  }
});

server.listen(3000, () => {
  console.log('Server started on port 3000');
});

https

In addition to the http module, Node.js also provides an https module for creating HTTPS servers and clients. Similar to http, we can also return different data based on different URL paths. However, it is important to note that HTTPS is an encrypted HTTP protocol and it requires a certificate to work properly.

The following is a simple example:

const https = require('https');
const fs = require('fs');

const options = {
  key: fs.readFileSync('server.key'),
  cert: fs.readFileSync('server.cert')
};

const server = https.createServer(options, (req, res) => {
  if (req.url === '/') {
    res.end('Hello, world (HTTPS)!');
  } else if (req.url === '/about') {
    res.end('About us (HTTPS)');
  } else {
    res.end('Not found (HTTPS)');
  }
});

server.listen(3000, () => {
  console.log('Server started on port 3000 (HTTPS)');
});

net

In addition to the http and https modules, Node.js also provides the net module for creating TCP servers and clients end. Through the net module, we can realize network transmission, Socket communication and other functions. For example, we can implement functions such as multi-person chat rooms and online games through Socket communication.

The following is a simple example:

const net = require('net');

const server = net.createServer((socket) => {
  socket.write('Echo server\r\n');
  socket.pipe(socket);
});

server.listen(1337, '127.0.0.1', () => {
  console.log('Server started on port 1337');
});

dns

In Node.js, dns is a built-in module used for domain name resolution. Through the dns module, we can easily implement the function of resolving domain names into IP addresses and provide external interfaces.

Here is a simple example:

const dns = require('dns');

dns.lookup('www.google.com', (err, address) => {
  console.log('address: %j', address);
});

url

In Node.js, url is a built-in module for URL parsing. Through the url module, we can easily get various parts of the URL, such as protocol, host name, port number, path, query parameters, etc.

Here is a simple example:

const url = require('url');

const myUrl = url.parse('https://www.baidu.com/search?q=node.js');

console.log('protocol:', myUrl.protocol); // https:
console.log('hostname:', myUrl.hostname); // www.baidu.com
console.log('port:', myUrl.port); // null
console.log('pathname:', myUrl.pathname); // /search
console.log('query:', myUrl.query); // q=node.js

querystring

In Node.js, querystring is a built-in module for parsing and formatting query strings. Through the querystring module, we can easily obtain each parameter in the query string and provide an interface to the outside world.

The following is a simple example:

const querystring = require('querystring');

const myQuery = querystring.parse('q=node.js&from=google');

console.log(myQuery); // { q: 'node.js', from: 'google' }

const myString = querystring.stringify(myQuery);

console.log(myString); // q=node.js&from=google

Summary

Through the above introduction, we can see that in Node.js, there are many built-in modules that can be used with interact with external interfaces. These modules can meet most of our needs and avoid introducing too many dependencies. Of course, Node.js also supports third-party modules, and we can also choose appropriate third-party modules according to specific circumstances.

Providing external interfaces is an important part of Web development. The powerful interface function of Node.js provides great help for our development.

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