Js judge ie version number of the simple implementation code

JQuery 2.0 removes the judgment of browser version number (it recommends feature detection), here is a native judgment method written by foreigners, this code is really clever! Both brief, backwards compatible! The general approach is: regular search USER_AGENT;
However, due to historical reasons, USER_AGENT has always been inaccurate, and has been changed in a mess by various manufacturers. :
Such as:

Consumer: Mozilla / 5.0 (compatible; MSIE 10.0; Windows NT 6.2; WOW64. Trident / 6.0)

IE11: Mozilla/5.0 (Windows NT 6.3; Trident / 7.0; The rv 11.0) like Gecko

What the hell are these strings... Who knows what IE12 will become!!
So using feature detection, or user-agent detection, is neither reliable nor backward compatible!

The following code is highly recommended!

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;
        } ());
        alert(_IE);