Javascript: addEvent

gistfile1

var addEvent = (function( window, document ) {
	if ( document.addEventListener ) {
		return function( elem, type, cb ) {
			if ( elem && !elem.length ) {
				elem.addEventListener(type, cb, false );
			}
			else if ( elem && elem.length ) {
				var len = elem.length;
				for ( var i = 0; i < len; i++ ) {
					addEvent( elem[i], type, cb );
				}
			}
		};
	}
	else if ( document.attachEvent ) {
		return function ( elem, type, cb ) {
			if ( elem && !elem.length ) {
				elem.attachEvent( 'on' + type, function() { return cb.call(elem) } );
			}
			else if ( elem.length ) {
				var len = elem.length;
				for ( var i = 0; i < len; i++ ) {
					addEvent( elem[i], type, cb );
				}
			}
		};
	}
})( this, document );