IE版本判断

gistfile1.js

var _IE = (function() {
  var 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 : false;
}());