Ajax style file uploading using hidden iframe
- By Viral Patel on November 18, 2008
- AJAX, How-To, JavaScript, Tutorial
File uploading using AJAX is not possible. AJAX doesn’t actually post forms to the server, it sends selected data to the server in the form of a POST or GET request. As javascript is not capable of grabbing the file from the users machine and sending it to the server, it’s just not possible with AJAX. You have to resort to regular old form submit.
If you have read/seen it somewhere, then it is not through AJAX. File uploading occurs through an iframe in this case. You have to use a iframe to upload the files. So, you can use iframe to asynchronous upload (Like AJAX , but its not AJAX).
How file uploading is done in Gmail? Use following JavaScript function, if you want to achieve same functionality.
<html>
<script language="Javascript">
function fileUpload(form, action_url, div_id)
{
// Create the iframe...
var iframe = document.createElement("iframe");
iframe.setAttribute("id","upload_iframe");
iframe.setAttribute("name","upload_iframe");
iframe.setAttribute("width","0");
iframe.setAttribute("height","0");
iframe.setAttribute("border","0");
iframe.setAttribute("style","width: 0; height: 0; border: none;");
// Add to document...
form.parentNode.appendChild(iframe);
window.frames['upload_iframe'].name="upload_iframe";
iframeId = document.getElementById("upload_iframe");
// Add event...
var eventHandler = function() {
if (iframeId.detachEvent)
iframeId.detachEvent("onload", eventHandler);
else
iframeId.removeEventListener("load", eventHandler, false);
// Message from server...
if (iframeId.contentDocument) {
content = iframeId.contentDocument.body.innerHTML;
} else if (iframeId.contentWindow) {
content = iframeId.contentWindow.document.body.innerHTML;
} else if (iframeId.document) {
content = iframeId.document.body.innerHTML;
}
document.getElementById(div_id).innerHTML = content;
// Del the iframe...
setTimeout('iframeId.parentNode.removeChild(iframeId)', 250);
}
if (iframeId.addEventListener)
iframeId.addEventListener("load", eventHandler, true);
if (iframeId.attachEvent)
iframeId.attachEvent("onload", eventHandler);
// Set properties of form...
form.setAttribute("target","upload_iframe");
form.setAttribute("action", action_url);
form.setAttribute("method","post");
form.setAttribute("enctype","multipart/form-data");
form.setAttribute("encoding","multipart/form-data");
// Submit the form...
form.submit();
document.getElementById(div_id).innerHTML = "Uploading...";
}
</script>
<!-- index.php could be any script server-side for receive uploads. -->
<form>
<input type="file" name="datafile" /></br>
<input type="button" value="upload"
onClick="fileUpload(this.form,'index.php','upload'); return false;" >
<div id="upload"></div>
</form>
</html>
Get our Articles via Email. Enter your email address.
Hi! Thanks for such a nice tip, although data seem posted but one problem is that IFrame start downlaoding in IE what could be the issue is ?
Thanks for sharing! I used your code as a base and mixed in some jquery methods for the binding and it worked perfectly on ie and firefox.
You should add the var keyword to lines 31,33,35 before the content variable as IE7 throws an error. Very useful script though.
George
hm, can you show an example of a server-side script for receiving the upload.
This is awesome. Works great. Thank you!
I am unable to implement the server side script. In the server side script i gave my action class name but it throws an error. Can you please give me some example of how to implement the server side scripting
Very nice and easy to understand code. Thanks for sharing.
What should I do if I want to know when the uploading is done (e.g. to display new content to users) or to display a file-size-over-limit message to users?
Many thanks,
Fantab