JavaScript: Get IE version

getIEVer.js

// Returns the version of Internet Explorer or a -1
// (indicating the use of another browser).
function getIEVer() {
	var rv = -1; // Return value assumes failure.
	if (navigator.appName == 'Microsoft Internet Explorer') {
		var ua = navigator.userAgent;
		var re = new RegExp("MSIE ([0-9]{1,}[\.0-9]{0,})");
		if (re.exec(ua) !== null) {
			rv = parseFloat(RegExp.$1);
		}
	}
	return rv;
}