2019-08-15 koa各种小知识

1

const Koa=require('koa');
const mysql =require('promise-mysql');

const server=new Koa();
server.use(async (ctx, next)=>{   //koa只能用use,没有get,post方法，而是要用koa-router
                         //use只有一个参数，那就中间件函数       
    let db = await mysql.createPool({
        host:'localhost',
        user:'root',
        password:'123456',
        database:'computer'
    })

    let data=await db.query('update user_table set name=? where id=?',['dream1','2'])
    ctx.body=data
});
server.listen(3000)

const Koa=require('koa')
const fs=require('promise-fs')

const server=new Koa()
server.use(async (ctx,next)=>{
    const txt=await fs.readFile("./1.txt")
    ctx.txt=txt.toString()
    await next()
})

server.use(async (ctx,next)=>{
    await fs.appendFile('./log.txt',`[${new Date().toGMTString()}] ${ctx.method} ${ctx.url}\n`)
    await next()
})

server.use((ctx,next)=>{
    ctx.body=ctx.txt
})

server.listen(3000)

2. koa-better-body 和ctx.redirect()重定向的使用

const Koa=require('koa')
const Router=require('koa-router')
const fs=require('promise-fs')
const bodyParser=require('koa-better-body')

const server=new Koa()
const router=new Router();

let login=false;
server.use(bodyParser())
server.use(async (ctx,next)=>{
    await next()
})

server.use(router.routes())

router.get('/',(ctx,next)=>{
    console.log(111)

    if(!login){
        console.log(222)
        ctx.redirect('/login')

    }
     console.log(444)
    ctx.body="欢迎"
})

router.get('/login',async (ctx,next)=>{
    const data=await fs.readFile('./static/login.html')
    ctx.body=data.toString()
})

router.post('/login',(ctx,next)=>{
    console.log(123)
    console.log(ctx.request.fields)
    login=true
    ctx.redirect('/')
})

server.listen(3000)

3. koa下载文件，自定义文件名称

const Koa=require('koa')
const Router=require('koa-router')
const fs=require('promise-fs')

const server=new Koa();
const router=new Router()

router.get('/download', async (ctx,next)=>{
    ctx.attachment("ltf.txt")
    const data=await fs.readFile('./static/login.html')
    ctx.body=data
    
})

server.use(router.routes())

server.listen(3000)

4.下载的文件由程序动态指定内容就要用内存流

const Koa=require('koa');
const Router=require('koa-router');
const fs=require('promise-fs');
const MemoryStream=require('memorystream');

let server=new Koa();
server.listen(8080);

let router=new Router();

router.get('/b', async ctx=>{
  let stream=new MemoryStream();
  ctx.attachment('20170813.txt');
  ctx.body=stream;

  stream.write('aaa');
  stream.write('bbb');

  stream.end();
});

server.use(router.routes());

5 操作http的头信息

const Koa=require('koa');
const Router=require('koa-router');
const fs=require('promise-fs');
const MemoryStream=require('memorystream');

let server=new Koa();
server.listen(8080);

let router=new Router();

router.get('/', async ctx=>{
  //console.log(ctx.headers);
  //console.log(ctx.headers['host']);
  //console.log(ctx.get('host'));

  ctx.set('name', 'blue');
  ctx.set('age', '18');
  ctx.set('set-cookie', 'type=12');

  ctx.body='welcome';
});

server.use(router.routes());

6.下载大文件的时候返回流给body就行

const Koa=require('koa');
const Router=require('koa-router');
const fs=require('promise-fs');
const MemoryStream=require('memorystream');

let server=new Koa();
server.listen(8080);

let router=new Router();

router.get('/', async ctx=>{
  ctx.attachment('aaa.txt');

  // ctx.body=await fs.readFile('static/1.txt');
  ctx.body=await fs.createReadStream('static/1.txt');
});

server.use(router.routes());

7 koa向第三方网站请求数据

const Koa=require('koa');
const request=require('./libs/request');

let server=new Koa();
server.listen(8080);

// http://ip.taobao.com/service/getIpInfo.php?ip=[ip地址字串]

server.use(async ctx=>{
  let url=`http://ip.taobao.com/service/getIpInfo.php?ip=202.13.96.75`;

  try{
    let data=await request(url);
    let json=JSON.parse(data.toString());

    ctx.body=json;
  }catch(e){
    ctx.body='地址解析失败';
  }
});

//request.js文件
const http=require('http');

module.exports=function (url){
  return new Promise((resolve, reject)=>{
    let req=http.request(url, res=>{
      let arr=[];

      res.on('data', data=>{
        arr.push(data);
      });
      res.on('end', ()=>{
        let buffer=Buffer.concat(arr);

        resolve(buffer);
      });
    });
    req.end();

    req.on('error', err=>{
      reject(err);
    });
  });
};

8. koa-static静态资源访问，设置缓存有效时间，

const Koa=require('koa')
const static=require('koa-static')
const Router=require('koa-router')

let server=new Koa();

server.listen(8080);

let router=new Router()

router.all(/\.(jpg|png|gif)$/i,static('./static',{
  maxage:60*86400*1000
}))

router.all(/\.js$/i,static('./static',{
  maxage:1*86400*1000
}))

router.all(/\.css$/i,static('./static',{
  maxage:7*86400*1000
}))

router.all(/\.html?$/i,static('./static',{
  maxage:1*86400*1000
}))

router.all('*',static('./static',{
  maxage:7*86400*1000
}))

server.use(router.routes())
/* 
server.use(static('./static',{
  maxage:60*86400*1000,
  index:'index.html',//当别人访问/的时候
}))
 */

9. koa图片上传封装

const Koa = require('koa')
const Router = require('koa-router')
const static = require('koa-static')
const fs = require('promise-fs')
const upload = require('./lib/upload')
const path=require('path')

const server = new Koa()
const router = new Router()

router.post('/upload', ...upload({
     async success(ctx) {
        ctx.body = { e: 'suc' }
    }, async failed (err) {
        if (err == 'maxfilesize exceeded') {
            ctx.status = 406  //可以覆盖upload.js里面的
            ctx.body = { e: 'error', msg: '文件过大' }
        }else{
            ctx.body={e:"error",msg:"服务器错误"}
        }
    },
    path:path.resolve(__dirname,'upload'),
    maxFileSize:100*1024
}))


server.use(router.routes())

server.use(static('./static', {
    maxage: 7 * 3600 * 24 * 1000,
    index: 'form.html'
}))

server.listen(8080)

//  lib/upload.js
const convert=require('koa-convert')
const body=require('koa-better-body')
module.exports=function(options){
    return [async(ctx,next)=>{
        try{
          await next()
        }catch(e){
          if(e.message.startsWith('maxFileSize exceeded')){
              ctx.status=406
              options.failed &&await options.failed(ctx,'maxfilesize exceeded')
          }
          else{
              ctx.status=500
              ctx.body={e:"error",msg:"服务器错误"}
              options.failed && await options.failed(ctx,'server error')
          }
        }      
      },convert(body({
        uploadDir:options.path,
        maxFileSize:options.maxFileSize
      })),async (ctx,next)=>{
          console.log(ctx.request)
        options.success&&await options.success(ctx)
    }]
}