I’ve been bumping up against an interesting bug in Internet Explorer recently, and, having just found the solution, thought I’d share it with you.

The problem is that in Internet Explorer (tested 7 & 8), when your document is in quirks mode, uploading a file sometimes just sends through the file name, without the actual body of the request. Put the document into standards mode, and it all works. It should be noted that this is when you’re dynamically setting up the elements used with JavaScript.

The cause? In quirks mode, the enctype attribute isn’t supported. So whilst setting “encType” on the form element to the correct “multipart/form-data” will indeed set this attribute, it won’t actually cause the upload to include the file. Instead, you need to set the encoding attribute to this value, too. It certainly doesn’t help that the MSDN article on the <input type=”file”> element tells you to set “enctype”, but makes no mention of “encoding”.

• MSDN: ‘Encoding’ property
• MSDN: ‘Enctype’ property
• MSDN: <input type=”file”> element

I couldn’t find any reference to this problem on the intertubes (although maybe I just didn’t look hard enough), so hopefully this will help someone.

Sometimes, you’ll want to allow users the ability to print only a part of your page; for example, a table but not the various links around the page. It’s possible to use a printing stylesheet, but this can cause severe headaches when you need different parts printed at different times. Really, we want to be able to just say element.printElement(), and have it just work. That’s what the MooTools function below does. It’s loosely based around the concepts outlined at this website.

Element.implement({
	printElement: function() {
		var strName = 'printer-' + (new Date()).getTime(),
		styles = $$('link[type=text/css]').clone(),
		title = document.title,
		that = this,
		iframe = new IFrame({
			name: strName,
			styles: {
				width: 1,
				height: 1,
				position: 'absolute',
				left: -9999
			},
			events: {
				load: function() {
					var doc = this.contentDocument || window.frames[strName].document;
					doc.title = title;
					$(doc.body).adopt(styles, that.clone());
					this.contentWindow.focus(); // IE requires us to focus before printing, or the parent prints.
					this.contentWindow.print();
				}
			}
		}).inject($(document.body));
		iframe.dispose.delay(15000); // Destroy the iframe in 15s so that it doesn't hang around.
	}
});

Often, you will need to prevent users from entering data that doesn’t conform to a specific pattern. For example, you may want to allow users to enter only numbers or only valid email addresses. To this end, I’ve written a little utility function that returns the “standardised” version of a string, according to the regex you supply.

String.implement({
	limitContent: function(allowedRegex) {
		return $splat(this.match(allowedRegex)).join('');
	}
});

Basically, the function takes the result of evaluating the regular expression on the string, converts it into an array if it isn’t one, and then joins the array’s elements together with an empty string.

Examples:

console.log("12345".limitContent(/.{4}/)); // Only allow four characters
console.log("joe@mail.com".limitContent(/[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}/)); // Only allow email addresses

I just tried out Google Wave on the iPhone. Interestingly, despite an initial “your browser is not supported” message, the actual system sports a rather snazzy app-like interface on the iPhone.

I’ll be interested to see what kind of support Wave will ‘officially’ have on mobile platforms, and perhaps even more interested in what ‘unofficial’ support there’ll be.