node.js之koa2知识点总结

const Koa = require('koa')
const app = new Koa()

app.use(async ctx => {
    ctx.body = 'Hello Koa2'
})

app.listen(3000)
console.log('server is running at port 3000')

const Koa = require('koa')
const app = new Koa()
const Router = require('koa-router')

// 路由
let router = new Router({
    // 前缀 
    prefix : '/nodejs'
})

router
    .get('/index', async ctx => {
    let html = '<a href="https://www.abc.edu.cn">商贸学院</li>'
    ctx.body = html
})

app.use(router.routes()).use(router.allowedMethods())

app.listen(3000)
console.log('server is running at port 3000')

const Koa = require('koa')
const app = new Koa()
const Router = require('koa-router')

// 子路由
let index = new Router()
index.get('/index', async ctx => {
    let html = '<a href="https://www.abc.edu.cn">商贸学院</li>'
    ctx.body = html
})

// 子路由
let error = new Router()
error.get('/error', async ctx => {
    let html = 'Error Page'
    ctx.body = html
})

// 装载路由
let router = new Router()
router.use(index.routes(), index.allowedMethods()) // 访问路径：/index
router.use('/koa2', error.routes(), error.allowedMethods()) // 访问路径：/koa2/error

app.use(router.routes()).use(router.allowedMethods())

app.listen(3000)
console.log('server is running at port 3000')

const Koa = require('koa')
const app = new Koa()
const bodyParser = require('koa-bodyparser')

// 使用ctx.body解析中间件
app.use(bodyParser())

app.use(async ctx => {
    // GET请求
    if (ctx.url == '/' && ctx.method == 'GET') {
        let html = `
          <form method="POST" action="/">
            用户: <input name="username" /><br/>
            密码: <input name="password" type="password"/><br/>
            <input type="submit"/>
          </form>
            `
        ctx.body = html
    } 
    // POST请求
    else if (ctx.url == '/' && ctx.method == 'POST') {
        let postData = ctx.request.body
        ctx.body = postData
    } 
    else {
        ctx.body = '<h1>404 Page Not Found</h1>'
    }
})

app.listen(3000)
console.log('server is running at port 3000')

const Koa = require('koa')
const app = new Koa()

app.use(async ctx => {
    // GET请求
    let url = ctx.url
    let ctx_query = ctx.query
    let ctx_querystring = ctx.querystring

    ctx.body = {
        url,
        ctx_query,
        ctx_querystring
    }
})

app.listen(3000)
console.log('server is running at port 3000')

const Koa = require('koa')
const path = require('path')
const static = require('koa-static')

const app = new Koa()

// 静态资源目录对于相对入口文件的路径
const staticPath = './static'

app.use(static(
    path.join( __dirname,  staticPath)
))

app.use( async ctx => {
    let html = 'YungFan'
    ctx.body = html
})

// 访问：http://localhost:3000/iOSer.png  http://localhost:3000/style.css  http://localhost:3000/method.js

app.listen(3000)
console.log('server is running at port 3000')

const Koa = require('koa')
const fs = require('fs')
const path = require('path')
const app = new Koa()
const Router = require('koa-router')
const koaBody = require('koa-body')

// koaBody 完成上传文件
app.use(koaBody({
    multipart: true,
    formidable: {
        maxFileSize: 5 * 1024 * 1024    // 设置上传文件大小最大限制，默认20M，这里设置为5M
    }
}))

app.use(async ctx => {
    // 单文件
    if (ctx.url == '/upload' && ctx.method == 'GET') {
        let html = `
          <form method="POST" action="/upload" enctype="multipart/form-data">
            <input type="file" name="file" id="file" value=""/><br/>
            <input type="submit"/>
          </form>
            `
        ctx.body = html
    }
    // 多文件
    else if (ctx.url == '/uploads' && ctx.method == 'GET') {
        let html = `
          <form method="POST" action="/uploads" enctype="multipart/form-data">
            <input type="file" name="file" id="file" value="" multiple="multiple" /><br/>
            <input type="submit"/>
          </form>
            `
        ctx.body = html
    }
    else if (ctx.url == '/upload' && ctx.method == 'POST') {
        // 上传单个文件
        const file = ctx.request.files.file // 获取上传文件
        // 创建可读流
        const reader = fs.createReadStream(file.path)
        // 上传路径
        let filePath = path.join(__dirname, 'upload/')
        // 检查路径是否存在
        checkDirExist(filePath)
        // 文件名
        const fileName = `${filePath}/${file.name}`
        // 创建可写流
        const upStream = fs.createWriteStream(fileName)
        // 可读流通过管道写入可写流
        reader.pipe(upStream)
        return ctx.body = "单文件上传成功！"
    }
    else if (ctx.url == '/uploads' && ctx.method == 'POST') {
        // 上传多个文件
        const files = ctx.request.files.file 
        for (let file of files) {
            // 里面操作和前面单文件一样
            const reader = fs.createReadStream(file.path)
            let filePath = path.join(__dirname, 'upload/')
            checkDirExist(filePath)
            const fileName = `${filePath}/${file.name}`
            const upStream = fs.createWriteStream(fileName)
            reader.pipe(upStream)
        }
        return ctx.body = "多文件上传成功！"
    }
    else {
        ctx.body = '<h1>404 Page Not Found</h1>'
    }
})

app.listen(3000)
console.log('server is running at port 3000')

// 判断文件夹是否存在，不存在则创建
function checkDirExist(path) {
    if (!fs.existsSync(path)) {
        fs.mkdirSync(path)
    }
}

const mysql = require('mysql')

let pools = {} // 连接池

let operation = (sql, host = '127.0.0.1') => {
    if (!pools.hasOwnProperty(host)) { // 是否存在连接池
        pools[host] = mysql.createPool({ // 不存在创建
            host: host,
            port: '3306',
            user: 'root',
            password: 'root',
            database: 'nodejsDB'
        })
    }

    return new Promise((resolve, reject) => {
        pools[host].getConnection((err, connection) => { // 初始化连接池
            if (err)
                console.log(err,'数据库连接失败')
            else
                connection.query(sql, (err, results) => { // 去数据库查询数据
                    connection.release() // 释放连接资源
                    if (err)
                        reject(err)
                    else
                        resolve(results)
            })
        })
    })
}

module.exports = operation

const Koa = require('koa')
const app = new Koa()
const Router = require('koa-router')
const dbTool = require('./dbTools') // 注意路径

let router = new Router()

router.get('/users/list', async (ctx, next) => {
    await dbTool(`select * from t_user`).then((res) => {
        console.log(res)
        ctx.body = res // 返回给前端的数据
    })

    await next()
})

app.use(router.routes()).use(router.allowedMethods())

app.listen(3000)
console.log('server is running at port 3000')