The XMLHttpRequest Level 2 standard (still a working draft) defines the FormData
interface. This interface enables appending File
objects to XHR-requests (Ajax-requests).
Btw, this is a new feature - in the past, the "hidden-iframe-trick" was used (read about that in my other question).
This is how it works (example):
var xhr = new XMLHttpRequest(), fd = new FormData(); fd.append( 'file', input.files[0] ); xhr.open( 'POST', 'http://example.com/script.php', true ); xhr.onreadystatechange = handler; xhr.send( fd );
where input
is a <input type="file">
field, and handler
is the success-handler for the Ajax-request.
This works beautifully in all browsers (again, except IE).
Now, I would like to make this functionality work with jQuery. I tried this:
var fd = new FormData(); fd.append( 'file', input.files[0] ); $.post( 'http://example.com/script.php', fd, handler );
Unfortunately, that won't work (an "Illegal invocation" error is thrown - screenshot is here). I assume jQuery expects a simple key-value object representing form-field-names / values, and the FormData
instance that I'm passing in is apparently incompatible.
Now, since it is possible to pass a FormData
instance into xhr.send()
, I hope that it is also possible to make it work with jQuery.
Update:
I've created a "feature ticket" over at jQuery's Bug Tracker. It's here: http://bugs.jquery.com/ticket/9995
I was suggested to use an "Ajax prefilter"...
Update:
First, let me give a demo demonstrating what behavior I would like to achieve.
HTML:
<form> <input type="file" id="file" name="file"> <input type="submit"> </form>
JavaScript:
$( 'form' ).submit(function ( e ) { var data, xhr; data = new FormData(); data.append( 'file', $( '#file' )[0].files[0] ); xhr = new XMLHttpRequest(); xhr.open( 'POST', 'http://hacheck.tel.fer.hr/xml.pl', true ); xhr.onreadystatechange = function ( response ) {}; xhr.send( data ); e.preventDefault(); });
The above code results in this HTTP-request:
This is what I need - I want that "multipart/form-data" content-type!
The proposed solution would be like so:
$( 'form' ).submit(function ( e ) { var data; data = new FormData(); data.append( 'file', $( '#file' )[0].files[0] ); $.ajax({ url: 'http://hacheck.tel.fer.hr/xml.pl', data: data, processData: false, type: 'POST', success: function ( data ) { alert( data ); } }); e.preventDefault(); });
However, this results in:
As you can see, the content type is wrong...
processData:false
is a step in the right direction (see pradeek's proposed solution). Now if I could manually set the "Content-Type" HTTP-request header... See my updated question for details.