Joshua Cody Joshua Cody - 1 year ago 150
Javascript Question

Using HTML5 file uploads with AJAX and jQuery

Admittedly, there are similar questions lying around on SO. But it seems none quite meet my requirements. Here is what I'm looking to do:

  • Upload an entire form of data, one piece of which is a single file

  • Work with Codeigniter's file upload library

Up until here, all is well. The data gets in my database as I need it. Good good. But I'd also like to submit my form via an AJAX post:

  • Using the native HTML5 File API, not flash or an iFrame solution

  • Preferably interfacing with the low-level .ajax jQuery method

I think I could imagine how to do this by auto-uploading the file when the field's value changes using pure javascript, but I'd rather do it all in one fell swoop on for submit in jQuery. I'm thinking it's not possible to do via query strings as I need to pass the entire file object, but I'm a little lost on what to do at this point. Am I chasing a unicorn here?

Thanks so much for any help you could give.

Answer Source

It's not too hard. Firstly, take a look at FileReader Interface.

So, when the form is submitted, catch the submission process and

var file = document.getElementById('fileBox').files[0]; //Files[0] = 1st file
var reader = new FileReader();
reader.readAsText(file, 'UTF-8');
reader.onload = shipOff;
//reader.onloadstart = ...
//reader.onprogress = ... <-- Allows you to update a progress bar.
//reader.onabort = ...
//reader.onerror = ...
//reader.onloadend = ...

function shipOff(event) {
    var result =;
    var fileName = document.getElementById('fileBox').files[0].name; //Should be 'picture.jpg'
    $.post('/myscript.php', { data: result, name: fileName }, continueSubmission);

Then, on the server side (i.e. myscript.php):

$data = $_POST['data'];
$fileName = $_POST['name'];
$serverFile = time().$fileName;
$fp = fopen('/uploads/'.$serverFile,'w'); //Prepends timestamp to prevent overwriting
fwrite($fp, $data);
$returnData = array( "serverFile" => $serverFile );
echo json_encode($returnData);

Or something like it. I may be mistaken (and if I am, please, correct me), but this should store the file as something like 1287916771myPicture.jpg in /uploads/ on your server, and respond with a JSON variable (to a continueSubmission() function) containing the fileName on the server.

Check out fwrite() and

On the above page it details how to use readAsBinaryString(), readAsDataUrl(), and readAsArrayBuffer() for your other needs (e.g. images, videos, etc).

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