How to detect IE11 from User Agent?

Pre-IE11 versions of Internet Explorer browser have a common pattern/string i.e. "MSIE" within their user agent string. But that is not the case with IE11.

IE11 user agent string

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

IE10 user agent string

Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/6.0)

Here is some JavaScript code to identify the version Internet Explorer from user agent string

var isIE11 =  navigator.userAgent.match(/Trident.*rv\:11\./);

var isIEButNotIE11 =  navigator.userAgent.match(/MSIE (\d+\.\d+)/);

This function can be used to get the version number of IE

function IEVersion() {

    var ieversion;

    if (/MSIE (\d+\.\d+);/.test(navigator.userAgent))
        ieversion = new Number(RegExp.$1);
    else if (navigator.userAgent.match(/Trident.*rv\:11\./))
        ieversion = 11;

    return ieversion;
}