const fileList = uploadFormData.get("fileList");
console.log(fileList);
const reader = new FileReader();
reader.readAsDataURL(fileList);
reader.onload = () => {
  imgBase64.value = reader.result;
  console.log(imgBase64.value);
  console.log(base64ToFile(imgBase64.value, fileList.name));
};
reader.onerror = function (err) {
  console.log(err);
};

const base64ToFile = (base64, fileName) => {
  let data = base64.split(",");
  let type = data[0].match(/:(.*?);/)[1];
  let suffix = type.split("/")[1];
  const bstr = window.atob(data[1]);
  let n = bstr.length;
  const u8arr = new Uint8Array(n);
  while (n--) {
    u8arr[n] = bstr.charCodeAt(n);
  }
  // 利用構造函數創建File文件對象
  const file = new File([u8arr], `${fileName}.${suffix}`, {
    type: type,
  });
  return file;
};