const os = require('os');

const path = require('path');

const koaBody = require('koa-body');

const Koa = require('koa');

const app = new Koa();

const fs = require("fs");

const main = async function(ctx) {

  //const tmpdir = os.tmpdir(); //返回系统临时文件

  const tmpdir = path.join(__dirname, "static");	

  const filePaths = [];

  const files = ctx.request.files || {};

  const params = ctx.request.body

	 console.log(params);

   for (let key in files) {

   	const file = files[key];

   	if(Object.prototype.toString.call(file) == '[object Array]'){

   		for(var j = 0; j < file.length; j++ ){

   			witeFile(file[j]);

   		}

   	}else{

   		witeFile(file);

   }

  }

  function witeFile(file){

  	const filePath = path.join(tmpdir, file.name);

    const reader = fs.createReadStream(file.path);

    const writer = fs.createWriteStream(filePath);

    reader.pipe(writer);

    filePaths.push(filePath);

  }

  ctx.body = filePaths;

};

app.use(koaBody({ multipart: true }));

app.use(main);

app.listen(3000);

		<form action="http://localhost:3000/" method="post" enctype="multipart/form-data">

			<input type="text"	 name="name" id="" value="姓名" />

			<input type="text"	 name="pwd" id="" value="123456" />

			<input type="file" name="file" id="file" value="" multiple="multiple" />

			<input type="submit" value="提交"/>

		</form>　　

$("#file")[0].onchange = function(e){

			console.log(this.files);

			var filse = this.files;

			var fd = new FormData();

			fd.append("file",filse[0]);

			$.ajax({

				type:"post",

				data:fd,

				processData:false,

				contentType:false,

				url:"http://192.168.20.104:3000",

			}).then(function(ret){

				console.log(ret);

			}).catch((e)=>{

				console.log(e);

			})

		}

const multiparty = require('multiparty');

router.post('/file', function(req, res, next) {

    //生成multiparty对象，并配置上传目标路径

    const form = new multiparty.Form()

    // //设置编辑

    form.encoding = 'utf-8'

    // //设置文件存储路径

    form.uploadDir = "./public/static/"

    // //设置单文件大小限制

    //form.maxFilesSize = 2 * 1024 * 1024

    // form.maxFields = 1000;  设置所以文件的大小总和

    // 上传完成后处理

    form.parse(req, (err, fields, files) => {

        if (err) {

            console.log("parse:",err);

            res.json(configVar.fileUp);

        } else {

            const inputFile = files.file[0];

            const uploadedPath = inputFile.path

            var  imgtype = inputFile.originalFilename;

            const typarr = imgtype.split(".");

            const typ = typarr[typarr.length -1];

            const nm =  new  Date().getTime()  +  '' +  Math.floor(Math.random()*1000000) ;

            console.log(fields.old);

            imgtype = nm + '.' + typ;

            const inPath = `./public/static/${imgtype}`; //重命名的路径

            // 判断是否存在./dist/static/files文件

            fs.stat('./public/static', (err, stats) => {

                if (JSON.stringify(stats) === undefined) {

                    fs.mkdirSync('./public/static')

                }

                storeFiles(uploadedPath, fields, inPath)

            });

        }

    });

    function storeFiles(uploadedPath, fields, inPath) {

        //重命名为真实文件名

        fs.rename(uploadedPath, inPath,  (err) => {

            if (err) {

                console.log("rename:",err);

                res.json(configVar.rename);

            } else {

                var ret  = {

                    data:inPath.substring(8)

                };

                Object.assign(ret , configVar.success);

                res.json(ret);

            }

        });

    }

});