javascript - 如何使用 wix 通过 sendgrid 发送附件文件

Question

我想通过https://sendgrid.com使用 wix.com 发送电子邮件，一切正常，但附件为空。为什么？

我通过发送网格获取文件并发送

<input type="file" id='uploadFile1' />
<div onclick='send()'>send</div>


<script>
import {fetch} from 'wix-fetch';  

function sendWithService(key, sender, recipient, subject, body, attach) {
 const url = "https://api.sendgrid.com/api/mail.send.json";

 const headers = {
   "Authorization": "Bearer " + key,
   "Content-Type": "application/x-www-form-urlencoded"
 };

 var contentfile = attach;
 const data = `from=${sender}&to=${recipient}&subject=${subject}&text=${body}&files[download.png]=${contentfile}`;

 const request = {
   "method": "post", 
   "headers": headers, 
   "body": data
 };

 return fetch(url, request).then(response => response.json());
}

function sendEmail(subject, body, attach) {
  const key = "FDkdfjls__MYUNIQKEY__dsfsdlfs__MYUNIQKEY__asfkjsdf3424";
  const sender = "my@email.com";
  const recipient = "my@email.co";
  return sendWithService(key, sender, recipient, subject, body, attach);
}

function send() {
  sendEmail('my subject', 'my text', document.getElementById('uploadFile1').files[0]).then(response => console.log(response));
}
</script>

此代码中的电子邮件和密钥已更改。

答案是{message: "success"}，信件正确到达主题和文本，但文件是空的。它由[object, object]或{}