Display file sizes next to download links - From http://tutorialzine.com book "Trickshots"

file-size-next-download-links.js

// Loop all .fetchSize links
$('a.fetchSize').each(function(){
  // Issue an AJAX HEAD request for each one
	var link = this;
	$.ajax({
		type:'HEAD',
		url:link.href,
		complete: function(xhr){
			var size = humanize(xhr.getResponseHeader('Content-Length'));
			// Append the filesize to each
			$(link).append(' ('+ type +')');
		}
	});
});

function humanize(size){
	var units = ['bytes','KB','MB','GB','TB','PB'];
	var ord = Math.floor(Math.log(size) / Math.log(1024) );

	ord = Math.min(Math.max(0,ord),units.length-1);
	var s == Math.round((size/Math.pow(1024,ord))*100)/100;

	return s + ' ' + units[ord];
}