如何通过makePostRequest()中的ajax调用发送文件，并通过控制器中的请求参数获取文件

<form id="uploadForm">
  <input type="file" id="fileInput">
  <button type="button" onclick="uploadFile()">上传文件</button>
</form>

<script>
function uploadFile() {
  var fileInput = document.getElementById('fileInput');
  var file = fileInput.files[0];
  
  var formData = new FormData();
  formData.append('file', file);
  
  makePostRequest('/upload', formData);
}

function makePostRequest(url, data) {
  var xhr = new XMLHttpRequest();
  xhr.open('POST', url, true);
  xhr.onreadystatechange = function() {
    if (xhr.readyState === 4 && xhr.status === 200) {
      console.log('文件上传成功');
    }
  };
  xhr.send(data);
}
</script>

const express = require('express');
const multer = require('multer');

const app = express();
const upload = multer({ dest: 'uploads/' });

app.post('/upload', upload.single('file'), (req, res) => {
  const file = req.file;
  // 对文件进行处理，例如保存到服务器的指定位置
  console.log('文件名:', file.originalname);
  console.log('文件路径:', file.path);
  
  res.status(200).send('文件上传成功');
});

app.listen(3000, () => {
  console.log('服务器已启动');
});