Javascript IE detection, why not use simple condit

Question

In order to detect IE most Javascript libaries do all sort of tricks.

• jQuery seem to add a temporary object into your pages's DOM to detect some features,
• YUI2 does regex on the user agent in its YAHOO.env.ua = function() (file yahoo.js)

After reading this answer it came in my mind that it's true, in order to detect simply IE in Javascript we could simply add to our pages:

<!--[if IE]><script type="text/javascript">window['isIE'] = true;</script><![endif]-->

<script type="text/javascript" src="all-your-other-scripts-here.js"></script>

Now the window.isIE variable is set for all our Javascript code, by simply doing:

if(window.isIE)
   ...

Beside the fact that this might result in being a pain because it has to be added in all pages, are there any issues/considerations I might be unaware of?

---

FYI: I know it's better to use object detection rather than browser detection, but there are cases where you still have to use browser detection.

Answer 1

navigator.userAgent exists if browser detection (rather than feature detection) is really needed, and jQuery uses it to get the information for the $.browser object. It's much nicer than having to include an IE-specific conditional comment in every page.

Answer 2

IE 11 has changed a lot and now many past methods of browser detection do not work. The below code works for IE 11 and earlier.

function isIE()
{
    var isIE11 = navigator.userAgent.indexOf(".NET CLR") > -1;      
    var isIE11orLess = isIE11 || navigator.appVersion.indexOf("MSIE") != -1;
    return isIE11orLess;
}

Answer 3

I think I have what you are looking for. You can get the Full Version of Internet Explorer as a string "AA.BB.CCCC.DDDD" using Javascript and clientCaps.

http://www.pinlady.net/PluginDetect/IE/

It appears to work for IE 5.5 and higher (including IE 10). It is immune to the navigator.userAgent/document mode/browser mode. There is no need for conditional comments, or any extra HTML elements. It is a pure Javascript solution.

I am not certain at this time how IE Mobile behaves, but you can always use a backup detection method in case this clientCaps method fails.

So far, I gotta say, it works pretty well.

Answer 4

var version = navigator.userAgent.match(/(msie) (\d+)/i);
console.log(version);

something quick I wrote quick after looking at this question in case anyone wants it.

** EDIT **

Per Johnny Darvall's comment below, I'm adding a link for anyone who is trying to sniff out Internet Explorer 11:

http://blogs.msdn.com/b/ieinternals/archive/2013/09/21/internet-explorer-11-user-agent-string-ua-string-sniffing-compatibility-with-gecko-webkit.aspx

Answer 5

This works quite well,
var isIe = !!window.ActiveXObject;

Answer 6

Here you can find some really simple hacks for browser-detecting: http://www.thespanner.co.uk/2009/01/29/detecting-browsers-javascript-hacks/

var isIE = IE='\v'=='v';