Simple include for JavaScript

include.js

var include = (function ()
{
	var knownPaths = {};

	return (
		function ( path )
		{
			if ( knownPaths[ path ] ) return;

			knownPaths[ path ] = true;

			var tag = document.createElement( "script" );
			tag.type = "text/javascript";
			tag.src = path;

			document.getElementsByTagName( "head" )[ 0 ].appendChild( tag );
		}
	);
})();