Node.js 各种操作

Node.js是一个基于Chrome V8引擎的JavaScript运行环境，它使得JavaScript可以在服务器端运行。以下是一些在Node.js中常见的操作和相应的代码示例：

1. 文件系统操作：

const fs = require('fs');
 
// 异步读取
fs.readFile('example.txt', 'utf8', (err, data) => {
  if (err) throw err;
  console.log(data);
});
 
// 同步读取
let data = fs.readFileSync('example.txt', 'utf8');
console.log(data);
 
// 异步写入
fs.writeFile('example.txt', 'Hello World!', (err) => {
  if (err) throw err;
  console.log('The file has been saved!');
});
 
// 同步写入
fs.writeFileSync('example.txt', 'Hello World!');
 
// 删除文件
fs.unlink('example.txt', (err) => {
  if (err) throw err;
  console.log('File deleted successfully');
});

2. 创建HTTP服务器：

const http = require('http');
 
const server = http.createServer((req, res) => {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
});
 
const port = 3000;
server.listen(port, () => {
  console.log(`Server running at http://localhost:${port}/`);
});

3. 使用Express框架创建Web应用：

const express = require('express');
const app = express();
 
app.get('/', (req, res) => {
  res.send('Hello World!');
});
 
app.listen(3000, () => {
  console.log('Server running on port 3000');
});

4. 使用Node.js处理网络请求：

const http = require('http');
 
http.get('http://example.com', (resp) => {
  let data = '';
  
  // 接收数据片段
  resp.on('data', (chunk) => {
    data += chunk;
  });
  
  // 数据接收完毕
  resp.on('end', () => {
    console.log(data);
  });
  
}).on("error", (err) => {
  console.log("Error: " + err.message);
});

5. 使用Node.js创建TCP服务器：

const net = require('net');
 
const server = net.createServer((socket) => {
  console.log('A client connected');
  
  socket.on('data', (data) => {
    console.log(data.toString());
    socket.write('Hello Client!');
  });
  
  socket.on('close', () => {
    console.log('A client disconnected');
  });
});
 
server.listen(1337, () => {
  console.log('Server listening on 1337');
});

6. 使用Node.js创建TCP客户端：

const net = require('net');
 
const client = net.createConnection({port: 1337, host: 'localhost'}, () => {
  console.log('Connected to server!');
});
 
client.on('data', (data) => {
  console.log(data.toString());
  client.end();
});
 
client.on('close', () => {
  console.log('Connect