Checking for a specific browser isn't recommended any more - feature detection is generally more useful. If you really need to detect IE11, the following page has an example script under the section on detecting IE x.x:
http://www.javascriptkit.com/javatutors/navigator.shtml
In case this link disappears in future, the script is as follows:
//userAgent in IE7 WinXP returns: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727)
//userAgent in IE11 Win7 returns: Mozilla/5.0 (Windows NT 6.3; Trident/7.0; rv:11.0) like Gecko
if (navigator.userAgent.indexOf('MSIE') != -1)
var detectIEregexp = /MSIE (\d+\.\d+);/ //test for MSIE x.x
else // if no "MSIE" string in userAgent
var detectIEregexp = /Trident.*rv[ :]*(\d+\.\d+)/ //test for rv:x.x or rv x.x where Trident string exists
if (detectIEregexp.test(navigator.userAgent)){ //if some form of IE
var ieversion=new Number(RegExp.$1) // capture x.x portion and store as a number
if (ieversion>=12)
document.write("You're using IE12 or above")
else if (ieversion>=11)
document.write("You're using IE11 or above")
else if (ieversion>=10)
document.write("You're using IE10 or above")
else if (ieversion>=9)
document.write("You're using IE9 or above")
else if (ieversion>=8)
document.write("You're using IE8 or above")
else if (ieversion>=7)
document.write("You're using IE7.x")
else if (ieversion>=6)
document.write("You're using IE6.x")
else if (ieversion>=5)
document.write("You're using IE5.x")
}
else{
document.write("n/a")
}
So to replace your function, you could use something like:
function isIE() {
if (navigator.userAgent.indexOf('MSIE') != -1)
return true;
var detectIEregexp = /Trident.*rv[ :]*(\d+\.\d+)/
return detectIEregexp.test(navigator.userAgent);
}