<form method="post" enctype="multipart/form-data" action="/api/upload">
  <input type="text" name="username">
  <input type="password" name="password">
  <input type="file" name="file">
  <input type="submit">
</form>

<!-- 获取上传文件转成formData类型的文件 -->
<input multiple id="file" name="file" type="file" />
<button id="btn">提交</button>

const oFile = document.getElementById('file')
const oBtn = document.getElementById('btn')

oBtn.addEventListener('click', () => {
  files = oFile.files
  const formData = new FormData()
  formData.append('file', files[0])
  formData.append('file1', files[1])

  fetch('/api/upload', {
    method: "POST",
    body: formData
  })
})

const fs = require('fs')
const path = require('path')
const FormData = require('form-data')
const express = require('express')
const fetch = require('node-fetch')
const router = express.Router()
const multipart = require('connect-multiparty');
var multipartMiddleware = multipart()

router.post('/upload', multipartMiddleware, function (req, res) {
  // console.log(req.body, req.files);

  const { path: filePath, originalFilename } = req.files.file
  const newPath = path.join(path.dirname(filePath), originalFilename)

  fs.rename(filePath, newPath, function (err) {
    if (err) {
      return;
    }
    else {
      const file = fs.createReadStream(newPath)
      const form = new FormData()
      form.append('file', file)

      fetch('http://localhost:8080/upload', {
        method: "POST",
        body: form
      })
    }
  })
  res.json({})
});

module.exports = router;