How can I upload files asynchronously with jQuery?
With HTML5 you can make file uploads with Ajax and jQuery. Not only that, you can do file validations (name, size, and MIME type) or handle the progress event with the HTML5 progress tag (or a div). Recently I had to make a file uploader, but I didn't want to use Flash nor Iframes or plugins and after some research I came up with the solution.
The HTML:
<form enctype="multipart/form-data"> <input name="file" type="file" /> <input type="button" value="Upload" /></form><progress></progress>First, you can do some validation if you want. For example, in the .on('change') event of the file:
$(':file').on('change', function () { var file = this.files[0]; if (file.size > 1024) { alert('max upload size is 1k'); } // Also see .name, .type});Now the $.ajax() submit with the button's click:
$(':button').on('click', function () { $.ajax({ // Your server script to process the upload url: 'upload.php', type: 'POST', // Form data data: new FormData($('form')[0]), // Tell jQuery not to process data or worry about content-type // You *must* include these options! cache: false, contentType: false, processData: false, // Custom XMLHttpRequest xhr: function () { var myXhr = $.ajaxSettings.xhr(); if (myXhr.upload) { // For handling the progress of the upload myXhr.upload.addEventListener('progress', function (e) { if (e.lengthComputable) { $('progress').attr({ value: e.loaded, max: e.total, }); } }, false); } return myXhr; } });});As you can see, with HTML5 (and some research) file uploading not only becomes possible but super easy. Try it with Google Chrome as some of the HTML5 components of the examples aren't available in every browser.
2019 Update: It still depends on the browsers your demographic uses.
An important thing to understand with the "new" HTML5 file API is that it wasn't supported until IE 10. If the specific market you're aiming at has a higher-than-average propensity toward older versions of Windows, you might not have access to it.
As of 2017, about 5% of browsers are one of IE 6, 7, 8 or 9. If you head into a big corporation (e.g., this is a B2B tool or something you're delivering for training) that number can skyrocket. In 2016, I dealt with a company using IE8 on over 60% of their machines.
It's 2019 as of this edit, almost 11 years after my initial answer. IE9 and lower are globally around the 1% mark but there are still clusters of higher usage.
The important take-away from this —whatever the feature— is, check what browser your users use. If you don't, you'll learn a quick and painful lesson in why "works for me" isn't good enough in a deliverable to a client. caniuse is a useful tool but note where they get their demographics from. They may not align with yours. This is never truer than enterprise environments.
My answer from 2008 follows.
However, there are viable non-JS methods of file uploads. You can create an iframe on the page (that you hide with CSS) and then target your form to post to that iframe. The main page doesn't need to move.
It's a "real" post so it's not wholly interactive. If you need status you need something server-side to process that. This varies massively depending on your server. ASP.NET has nicer mechanisms. PHP plain fails, but you can use Perl or Apache modifications to get around it.
If you need multiple file uploads, it's best to do each file one at a time (to overcome maximum file upload limits). Post the first form to the iframe, monitor its progress using the above and when it has finished, post the second form to the iframe, and so on.
Or use a Java/Flash solution. They're a lot more flexible in what they can do with their posts...
I recommend using the Fine Uploader plugin for this purpose. Your JavaScript code would be:
$(document).ready(function() { $("#uploadbutton").jsupload({ action: "addFile.do", onComplete: function(response){ alert( "server response: " + response); } });});