前端vue+express实现文件的上传下载示例

yarn init -yyarn add express nodemon -Dvar express = require("express");const fs = require("fs");var path = require("path");const multer = require("multer"); //指定路径的var app = express();app.use(express.json());app.use(express.urlencoded({ extended: true }));// 前端解决跨域问题app.all("*", (req, res, next) => {  res.header("Access-Control-Allow-Origin", "*");  next();});// 访问静态资源app.use(express.static(path.join(__dirname)));// 文件上传app.post("/upload", multer({ dest: "./public" }).any(), (req, res) => {  const { fieldname, originalname } = req.files[0];  // 创建一个新路径  const name = fieldname.slice(0, fieldname.indexOf("."));  const newName = "public/" + name + path.parse(originalname).ext;  fs.rename(req.files[0].path, newName, function (err) {    if (err) {      res.send({ code: 0, msg: "上传失败", data: [] });    } else {      res.send({ code: 1, msg: "上传成功", data: newName });    }  });});// 文件下载app.get('/download', function(req, res) {  res.download('./public/test.xls');});// 图片下载app.get('/download/img', function(req, res) {  res.download('./public/2.jpg');});let port = 9527;app.listen(port, () => console.log(`端口启动: http://localhost:${port}`));

  <form action="http://localhost:9527/upload" method="POST" encType="multipart/form-data">      <input type="file" name="user"/>      <input type="submit" />    </form>

   <input type="file"  @change="changeHandler($event)"/>     changeHandler(event) {      let files  = event.target.files[0];      console.log("files",files)      let data = new FormData();      data.append(files.name,files);      console.log("data",data)      axios.post("http://localhost:9527/upload",data,{        headers:{          "Content-Type":"multipart/form-data"        }      }).then(res =>{        console.log("res",res)      })    },

    <input type="button" value="点击下载" @click="handleDownload">      handleDownload() {      axios({        method: 'get',        url: "http://localhost:9527/download",        data: {            test: "test data"        },        responseType: "arraybuffer" // arraybuffer是js中提供处理二进制的接口    }).then(response => {                // 用返回二进制数据创建一个Blob实例       if(!response) return;      let blob = new Blob([response.data], {                    type: "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",       }) // for .xlsx files                // 通过URL.createObjectURL生成文件路径                let url = window.URL.createObjectURL(blob)       console.log("url==========",url)              // 创建a标签                let ele = document.createElement("a")                ele.style.display = 'none'                // 设置href属性为文件路径，download属性可以设置文件名称                ele.href = url                ele.download = this.name                // 将a标签添加到页面并模拟点击                document.querySelectorAll("body")[0].appendChild(ele)                ele.click()                // 移除a标签                ele.remove()            });  },

   // 二进制流图片文件的下载  downLoadImg() {     axios({        method: 'get',        url: `http://localhost:9527/download/img`,        responseType: 'arraybuffer',        params: {          id: 12        }      }).then(res => {        var src = 'data:image/jpg;base64,' + btoa(new Uint8Array(res.data).reduce((data, byte) => data + String.fromCharCode(byte), ''))       // this.srcImg = src // 图片回显        var a = document.createElement('a')        a.href = src        a.download = '2.jpg'        a.click()        a.remove()      })    }