/**
 *判断IE版本号
 * @param 
 * @arrange (512.笔记) jb51.cc
 **/
// ----------------------------------------------------------
// 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
// ----------------------------------------------------------
    
var ie = (function(){ 
    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; 
}());
// 来自：编程之家 jb51.cc（jb51.cc）