代码均在js文件中, 运行： $node xxx.js

注意输入命令行时要进入当前文件夹，$pwd为当前路径，再$cd 路径

nodejs

1. http

const http = require('http');
const server = http.createServer();
server.listen('3000',()=>{
    console.log('listening on http://localhost:3000');
    //打印出来则创建成功
});
server.on('request', (req,res)=>{
     //当request请求，调用该函数
     res.end('hello world');
     //response返回字符串给浏览器
    //这里不能用send，send方法由express框架提供
});

2.fs

const fs = require('fs');
//路径写成'./a.txt或者a.txt'为当前文件夹下的a.txt
//不能写成'/a.txt'，/表示根目录(C:\，D:\等等)
fs.writeFile('./a.txt','aaaa', 'utf-8', (err) =>{
    if(err) throw err;
    console.log('写入内容:aaaa, utf-8格式, err为null');
});
fs.readFile('./a.txt', 'utf-8', (err, data)=>{
    if(err) throw err;
    console.log("a.txt内容为：" + data);
    //a.txt内容为：aaaa
});

express框架

1.

const express = require('express');
const app = express();
app.listen(3000, () => {
    console.log('Example app listening on port 3000!');
    //http://localhost:3000
});

//app.use((req,res,next)=>{...})：如果前面不加路径，那么所有路径访问前都会执行一遍该函数
//http://localhost:3000/index
app.use('/index', (req, res, next)=>{
    console.log('1:/index的use中间件请求');
    next();
    //需要加next()，不然下面的/index路径函数不会执行
});

//发送get请求时执行
app.get('/index',(req, res)=>{
    console.log('2:get请求');
    res.send('hello world');
});
//发送post请求时执行
// app.post('/',(req, res)=>{
//     console.log('post请求');
// });

2.router

子路由

//2.js
const router = require('./3')
const express = require('express')
const app = express();
app.listen(3000,() => {
    console.log('http://localhost:3000');
})
app.use('/a', router);
//http://localhost:3000/a/index返回信息
//3.js
const express = require('express')
const router = express.Router()
router.get("/index", (req,res,next)=>{
    res.send("我是index");
    console.log(1);
})
module.exports = router;

2.js

const express = require('express');
const app = express();
const router = require('./3');
app.listen(3000, () => {
    console.log('http://localhost:3000');
});
app.use('/', router);
//访问http://localhost:3000，先调用router
app.get('/', () => {
    console.log('第二');
});

3.js

const express = require('express');
const router = express.Router();
router.get('/', (req, res, next) => {
  console.log('第一')
  res.send('Hello World!');
  next();
  //中间件一定要记得next
});
module.exports = router;