JavaScript IE Version Detection, IE6-10 and IE Mobile

gistfile1.js

// ----------------------------------------------------------
// A short snippet for detecting versions of IE in JavaScript
// without resorting to user-agent sniffing
// ----------------------------------------------------------
// If you're not in IE (or IE version is less than 5) then:
//     ie === undefined
// If you're in IE (>=5) then you can determine which version:
//     ie === 7; // IE7
// Thus, to detect IE:
//     if (ie) {}
// And to detect the version:
//     ie === 6 // IE6
//     ie > 7 // IE8, IE9 ...
//     ie < 9 // Anything less than IE9
// ----------------------------------------------------------

// UPDATE: Now using Live NodeList idea from @jdalton

var ie = (function(){

    if (/*@cc_on!@*/true) return undef;

    var undef,
        v = 3,
        div = document.createElement('div'),
        all = div.getElementsByTagName('i');
    
    while (
        div.innerHTML = '<!--[if gt IE ' + (++v) + ']><i></i><![endif]-->',
        all[0]
    );
    
    return v > 4 ? v : undef;
    
}());

Sometimes I see "Unable to get property '1' of undefined or null reference" because
/IEMobile/(\d+.?(\d+)?)/.exec( navigator.userAgent ) is null
if "IEMobile" string is not exists in the navigator.userAgent.
I have used a code below for resolving of problem:

var ieMobile = /IEMobile/(\d+.?(\d+)?)/.exec( navigator.userAgent );
ieMobile = ( !! window.ActiveXObject && ieMobile && (ieMobile.length >= 2) && +( ieMobile[1] ) ) || NaN;