One of the lesser known HTML5 JavaScript goodies is the document.head DOM tree accessor, which is a more efficient (and easier to type) alternative to document.getElementsByTagName('head')[0].

The head element of a document is the first head element that is a child of the html element, if there is one, or null otherwise. The head attribute, on getting, must return the head element of the document (a head element or null).

Native support for document.head is very easy to detect:

if (document.getElementsByTagName('head')[0] === document.head) {
	// Native support
}

Emulating it is also very straightforward. Just put the following snippet in your JavaScript code:

document.head = document.head || document.getElementsByTagName('head')[0];

If you don’t care about JSLint booing at your code, you could also do this instead (which is slightly more efficient):

document.head || (document.head = document.getElementsByTagName('head')[0]);

After that, go ahead and use document.head all you want :)