if (newOptions.method === "POST" || newOptions.method === "PUT") {

if (!(newOptions.body instanceof FormData)) {
  newOptions.headers = {
    Accept: "application/json",
    "Content-Type": "application/json; charset=utf-8",
    ...newOptions.headers
  };
  newOptions.body = JSON.stringify(newOptions.body);
} else {
  // newOptions.body is FormData
  newOptions.headers = {
    Accept: "application/json",
    ...newOptions.headers
  };
}

}
antd pro 的代码示例中有关于 FormData的判断
this.props.form.validateFields((err, values) => {}）
values 是json对象。
怎么才能变为FormData?