Downloading and then uploading files with JavaScript

Question

Now first of all, I'm making a UserScript, meaning that I don't own the servers from which I download files or the servers to which I upload files.

So I need to download a file from a server (needs to be any type, not just text files), and then somehow submit that file to a file upload form on another website. Is that possible? At first I was wondering if I'd be able to submit the file directly from one server to the other, but I don't think that's possible.

So is there any way I can do this? I can use jQuery as well.

Here I found some thread about how do the uploading part: stackoverflow.com/questions/7690086/… — Zini
– Zini, Commented Apr 7, 2014 at 21:21

JackW · Accepted Answer · 2014-04-07 21:24:20Z

2

As long as you won't be blocked by XSS prevention, load the data using an XMLHttpRequest then post it to the other site.

Here is a very basic functional example:

var xhr = new XMLHttpRequest();
xhr.open("get", "http://www.example.com/file", true);
xhr.onload = function () {
  xhr.close();
  var xhr2 = new XMLHttpRequest();
  xhr2.open("post", "http://www.example2.com/form", true);
  xhr2.send(xhr.response);
}
xhr.send();

I would advise that you add some code to catch errors

For more details on XMLHttpRequests, the documentation can be found on MDN here, with instructions on how to use it on MDN here

answered Apr 7, 2014 at 21:24

JackW

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