Q:

How can I target only Internet Explorer 11 with JavaScript? 

What's the least error-prone way to target just IE11 with JavaScript? 
Note: This should really only be done for analytics or informing the user what browser they're using.  For everything else, there's feature detection. 

A:

The User-agent string for IE 11 is currently this one :
Mozilla/5.0 (Windows NT 6.3; Trident/7.0; rv 11.0) like Gecko

Windows 10 example:
Mozilla/5.0 (Windows NT 10.0; Trident/7.0; rv:11.0) like Gecko

Which means your can simply test, for versions 11.xx, 
var isIE11 = /Trident.*rv[ :]*11\./.test(navigator.userAgent);

As IE10 user agent was
Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)

it's probably also safe to bet on the fact that now Trident/X is supposed to be the real versionning. 

A:

IE11 keeps "Trident" in it's UA string, but drops MSIE.  A simple way to detect the browser is IE11 or above (IE12, IE13, etc) is:
var isAtLeastIE11 = !!( navigator.userAgent.match(/Trident/) && ! navigator.userAgent.match(/MSIE/));

If you want just IE11 (and you don't want future versions of IE to match), do this:
var isIE11 = !!( navigator.userAgent.match(/Trident/) && navigator.userAgent.match(/rv[ :]11/));

A:

var isIE11 = !! navigator.userAgent.match(/Trident\/7.0; rv 11/);

Source: http://www.nczonline.net/blog/2013/07/02/internet-explorer-11-dont-call-me-ie/

