Subir archivos con Ajax

//------------------------------------------------------------------------------------------------
// Engines      JavaScript 1.8.5+
//              JScript    10+
// Environments IE10+ FIREFOX4+ CHROME6+ OPERA12+ SAFARI5+
//------------------------------------------------------------------------------------------------
function upload 
(
      s // action-url
    , e // input file (id | element)
    , u // user
    , p // password
){
    if (typeof e != 'object')
        e = document.getElementById(e);
 
    var f, l = 0;

    if ((f = e.files) && (l = f.length) == 1) // HTML5! (FileList)
    {
        var h = new XMLHttpRequest();
  
        h.open('POST', s, false, u, p);
        h.setRequestHeader('Content-type', 'multipart/form-data');
        h.setRequestHeader('X-File-Name', (f = f[0]).name);
        h.setRequestHeader('X-File-Size', f.size);
        h.setRequestHeader('X-File-Type', f.type);
        h.send(f);
  
        return h.readyState == 4 && h.status == 200;
    }
 
    else if (l > 1)
    {
        f = [];
        for (var i = 0; i < l; ++i) f.push
        ({
               fileName : e.files[i].name
             , uploaded : upload(s, {files: [e.files[i]]}, u, p)
        });
  
        return f;
    }
 
    return false;
}

Uso con un sólo archivo:

<input id="file" type="file" />

if (upload('upload.php', 'file'))
{
    //TODO...
}

Uso con múltiples archivos:

<input id="files" type="file" multiple />

var r = upload('upload.php', 'files');

for (var i = 0, l = r.length; i < l; ++i) if (!r[i].uploaded) 
{
    alert('"' + r[i].fileName + '" Not uploaded correctly!');
    // TODO...
}

upload.php:

<?php

$hd   = getallheaders();
$name = $hd["X-File-Name"];

if (strlen($name) > 0)
{
    //$size = $hd["X-File-Size"];
    //$type = $hd["X-File-Type"];
    // TODO...

    $in  = fopen("php://input", "r");
    $out = fopen("upload/" . $name, "w");
    while($data = fread($in, 1024)) fwrite($out, $data);
    fclose($out);
    fclose($in);
}

?>

upload.jsp:

<%@ page import="java.io.*" %>
<%
    String fileName = request.getHeader("X-File-Name");
    if (fileName != null && fileName.length() > 0)
    {
        //String fileSize = request.getHeader("X-File-Size"); 
        //String fileType = request.getHeader("X-File-Type");    
        //TODO..
    
        FileOutputStream fos    = new FileOutputStream("webapps/test/upload/" + fileName);
        InputStream      is     = request.getInputStream();
        byte[]           buffer = new byte[1024];
        int              length = 0;
    
        while ((length = is.read(buffer)) != -1)
            fos.write(buffer, 0, length);
  
        fos.flush();
        fos.close();
    }
%>

upload.aspx:

<%@ Page Language="C#" %>
<%
if (Request.ContentLength > 0)
{
    string fileName = Request.Headers["X-File-Name"];

    if (fileName != null)
    {
        //string fileSize = Request.Headers["X-File-Size"];
        //string fileType = Request.Headers["X-File-Type"];
        //TODO...
         
        Request.SaveAs(Server.MapPath("/upload/") + fileName, false);
    }
}
%>

upload.asp:

<%@ Language="VBScript" %>
<%
Function Save (fileName, byteArray)
    on error resume next
    Dim  BinaryStream

    Set BinaryStream = CreateObject("ADODB.Stream")
   
    BinaryStream.Type = 1

    BinaryStream.Open
    BinaryStream.Write byteArray

    BinaryStream.SaveToFile Server.MapPath("upload") & "\" & fileName, 2
End Function

Dim strFileName
strFileName = Request.ServerVariables("HTTP_X-File-Name")

If (Len(strfileName) > 0) Then

    '... Request.ServerVariables("HTTP_X-File-Size")
    '... Request.ServerVariables("HTTP_X-File-Type")
    'TODO...

    Save strFileName, Request.BinaryRead(Request.TotalBytes)
End If
%>