Javascript: ie detect

gistfile1.js

// ----------------------------------------------------------
// 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 && ie === 6 // IE6
//     ie && ie > 7 // IE8, IE9 ...
//     ie && ie < 9 // Anything less than IE9
// ----------------------------------------------------------

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