What is the syntax to do a cross-domain XMLHTTPREQUEST to an FTP server?

Question

I have an webDav CORS plugin, which I can use to POST/PUT/GET/REMOVE/ALLDOCS files on a webDav server.

I now want to do the same for FTP, but I'm struggling to get the xmlhttprequest-syntax to work (I'm just getting error 0 ).

This page on Mozilla says it's possible to use xmlhttprequests for file and ftp as well, but I cannot find a working example or tutorial anywhere.

This is what I'm trying, which returns access to restricted URI denied

function reqListener () {
  console.log(this.responseText);
}

var oReq = new XMLHttpRequest();
oReq.onload = reqListener;
oReq.open("GET", "ftp://<username>:<passeword>@mydomain.de/folder/test.txt", true);
oReq.send();

I also tried a regular Ajax request

$.ajax({
  url: "ftp://sharedspace.domain.provider.com/folder/test.txt",
  type: "GET",
  async: true,
  dataType: "text",
  crossdomain : true,
  headers : {
    user: "<username>",
    password: "<password>"
  },
  success: function(e){
    console.log("success");
    console.log(e);
  },
  error: function(e){
    console.log("error");
    console.log(e);
  },
}); 

which also does not work, returning 0 status code.

Question:
What is the correct syntax to do a cross-domain XMLHTTPREQUEST for FTP.

Thanks!

EDIT:
The only useful link I found is this page here, but it's just bits and pieces of information and I couldn't puzzle them together.

EDIT
Maybe also useful link

Answer 1

Although the Mozilla MDN docs reference xmlHttpRequest supporting file and ftp none of the major browsers do AFAIK. It is one of the reasons why you need to serve your web projects from some sort of server, even if it is on the same machine, if you want to develop/test any xmlHttpRequest stuff since file:// doesn't work.

Microsoft specifically states that IE only supports http/https. The W3C spec for it also says that the spec is only for HTTP/HTTPS but that 'some implementations support protocols in addition to HTTP and HTTPS, but that functionality is not covered by this specification'.

As for CORS, it is specifically only for HTTP/HTTPS. The spec is all about using HTTP headers. See the W3C spec here. FTP doesn't have any equivalent type of header as HTTP.