Node.js的应用场景

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Node.js的应用场景：

1. 快速构建高性能的动态WEB应用
2. 构建命令行工具和程序
3. 实时Web应用(如多人游戏)
4. 实时通讯(如WebSocket服务器)
5. 创建TCP/UDP服务器
6. 定时任务和调度(如cron job)
7. 解析和生成PDF文件
8. 数据抓取和处理
9. 提供RESTful API
10. 开发桌面应用(使用Node-webkit或Electron)

解决方案和示例代码：

1. 快速构建高性能的动态WEB应用

const http = require('http');
 
http.createServer((req, res) => {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
}).listen(3000, () => {
  console.log('Server running at http://127.0.0.1:3000/');
});

2. 构建命令行工具和程序

#!/usr/bin/env node
console.log('Hello, world!');

3. 实时Web应用(如多人游戏)

const express = require('express');
const http = require('http');
const WebSocket = require('ws');
 
const app = express();
app.use(express.static('public'));
 
const server = http.createServer(app);
const wss = new WebSocket.Server({ server });
 
wss.on('connection', function connection(ws) {
  ws.on('message', function incoming(message) {
    console.log('received: %s', message);
  });
 
  ws.send('something');
});
 
server.listen(3000, function listening() {
  console.log('Listening on %d', server.address().port);
});

4. 实时通讯(如WebSocket服务器)

const WebSocket = require('ws');
 
const wss = new WebSocket.Server({ port: 8080 });
 
wss.on('connection', function connection(ws) {
  ws.on('message', function incoming(message) {
    console.log('received: %s', message);
  });
 
  ws.send('something');
});

5. 创建TCP/UDP服务器

const dgram = require('dgram');
const server = dgram.createSocket('udp4');
 
server.on('message', (msg, rinfo) => {
  console.log(`server got: ${msg} from ${rinfo.address}:${rinfo.port}`);
});
 
server.on('listening', () => {
  const address = server.address();
  console.log(`server listening ${address.address}:${address.port}`);
});
 
server.bind(41234);

6. 定时任务和调度(如cron job)

const CronJob = require('cron').CronJob;
 
new CronJob({
  cronTime: '* * * * * *',
  onTick: function() {
    console.log('you task');