get Internet Explorer version through javascript

Effective way to get Internet Explorer version through Javascript is

function getIEVersion() {
// Returns the version of Internet Explorer or a -1
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;
}

Hope this helps!