Test for IE in JS using Conditional Comments

ieDetect.js

// Based on jamespadolsey's gist: https://gist.github.com/527683
// -----------------------------------------------------------------
// Was curious to see what method would yield the best 'performance'
// — turns out that using innerHTML and checking for text is
// marginally faster than using a Live NodeList.
//
// Of course, any performance gains can only be seen at 100+
// iterations, but still somewhat interesting.

(function (ie) {
   window[ie] = (function() {
    var ie = 3,
        p = document.createElement('p'),
        undefined;
      
    do {
      ie += 1;
      p.innerHTML = '<!--[if gt IE ' + ie + ']>IE<![endif]-->';
    } while (p.innerHTML === 'IE');

    return ie > 4 ? ie : undefined;
  }());
}('ieDetect'));