如何将 URL 中的图像附加到 FormData - Javascript

这是我的小 JavaScript 代码：

<script>

var formData = new FormData();

URL = "view.php?fetchImageById=1";

formData.append("imageFile", ....);

formData.append("author","user");
formData.append("description","image");

x=new XMLHttpRequest();
x.open("POST","upload.php",true);
x.setRequestHeader("Content-type", "multipart/form-data");
x.setRequestHeader("Content-Length",formData.length);
x.send(formData);
</script>

我不知道如何将 URL 附加到 formData。

你可以执行两个XMLHttpRequest()s；第一的GET请求图像作为Blob首先通过设置responseType to "blob";然后追加Blob响应FormData at POST

var formData = new FormData();   
URL = "view.php?fetchImageById=1";    
var x;

var request = new XMLHttpRequest();
request.responseType = "blob";
request.onload = function() {
  formData.append("imageFile", request.response);
  formData.append("author","user");
  formData.append("description","image");
  x = new XMLHttpRequest();
  x.open("POST","upload.php",true);
  x.setRequestHeader("Content-type", "multipart/form-data");
  x.setRequestHeader("Content-Length", formData.length);
  x.send(formData);
}
request.open("GET", URL);
request.send();