gistfile1.js

// ----------------------------------------------------------
// A short snippet for detecting versions of IE in JavaScript
// without resorting to user-agent sniffing
// ----------------------------------------------------------
// If you're not in IE (or IE version is less than 5) then:
//     ie === undefined
// If you're in IE (>=5) then you can determine which version:
//     ie === 7; // IE7
// Thus, to detect IE:
//     if (ie) {}
// And to detect the version:
//     ie === 6 // IE6
//     ie > 7 // IE8, IE9 ...
//     ie < 9 // Anything less than IE9
// ----------------------------------------------------------

// UPDATE: Now using Live NodeList idea from @jdalton

var ie = (function(){

    var undef,
        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 : undef;
    
}());

Beware I wasted an awful of time on a IE issue related to requirejs trying to eval the last version of this gist submitted by @ecstaticpeon. So if you use this through requirejs and have a http://requirejs.org/docs/errors.html#fromtexteval error msg, it's definitely because of /*@cc_on I just added a space like this /* @cc_on and now the eval() pass. But I didn't tested on IE10 yet... anyway I don't like this conditional compilation stuff, I'll try to find something else.

@nrako: thanks for the heads up. But adding a space like you did does break the code. Try it on http://jsfiddle.net/P5z4N/4/

@nrako: here is a different version that might work for you :)

Try it on http://jsfiddle.net/e8G3S/1/

// Returns the version of Internet Explorer or a -1 (indicating the use of another browser)
function getInternetExplorerVersion(){
  var rv = -1; // Return value assumes failure.
  if (navigator.appName == 'Microsoft Internet Explorer'){
    var ua = navigator.userAgent;
    var re  = new RegExp("MSIE ([0-9]{1,}[\.0-9]{0,})");
    if (re.exec(ua) != null)
      rv = parseFloat( RegExp.$1 );
    }
  return rv;
}
function displayAlert(){
  var msg = "You're not using Internet Explorer.";
  var ver = getInternetExplorerVersion();
  if ( ver > -1 ){
    if ( ver <= 8.0 ){
      msg = "You're using Internet Explorer 8 or below" ;
    }
    else if ( ver >= 9.0 && ver < 10.0 ){
      msg = "You're using IE 9 or above";
    }
    else{
      msg = "You're using IE 10"; 
    }
  }
  alert( msg );
}

@adrien-be indeed it fail on IE10, the last code you sent is quite different it's solely useragent sniffing, and I still love the conditional comment better, I (and requirejs) just don't like the condition compilation stuff for IE10 detection.

Smaller yet? https://gist.github.com/devxdev/6506658

I Can't test I'm on Ubuntu. maybe smaller if undefined isn't required in the last ()

The expression in the while statement was done proper though for clarity I'd use a do-while.
Interesting :{D, fail on IE10, the last code you sent looks odd to me mainly because agent sniffing, I find the conditional comment interesting, I and requires just don't like the condition compilation stuff for IE10 detection. Because James uses a pre-increment to increment v:

(+/-) from the grade listed.

(+/-) from the grade listed.

(+/-) from the grade listed.

(+/-) from the grade listed.

I wanted this script to include IE10+11 as well, and my tests works fine by just returning document.documentMode instead of undefined, since it will be undefined for non-IE browsers anyway (I also prefer do...while...):

var ie = (function() {
  var v = 3
    , div = document.createElement( 'div' )
    , all = div.getElementsByTagName( 'i' )
  do
    div.innerHTML = '<!--[if gt IE ' + (++v) + ']><i></i><![endif]-->'
  while 
    (all[0])
  return v > 4 ? v : document.documentMode
}())

So I tried the code above, also davidhellsing's version, and I tested this on ie8, and it always says it's version 7, when it's 8. So I don't think this works on ie8.

Also, just tried it in ie10 and ie gets declared as undefined.

@ttfkam Best Solution for IE10+

For any future spelunkers, the @davidhellsing version just above works fine on IE8 through IE11

If I'm testing IE11, but it's forced into ie8 via 'IE=EmulateIE8', this solution from @davidhellsing still show the IE version as 8, not as 11. Any thoughts? I want to determine if it's really IE10/11.

You can use bowser.

This is slick!

Unfortunately IE>=10 don't have conditional comments

The best option for IE / Edge these days is probably Layout Engine or something similar that uses JavaScript to detect browser features.

User agents can be forged or altered so I wouldn't rely on UA sniffing.

Maybe help:

var ie = 'NotIE'; //IE5-11
if( !!document.compatMode ) {
if( !!(Math && Math.acosh) ) ie = 'EDGE 12';
if( !!document.uniqueID){
if(!!window.ActiveXObject){ ie = 11; }
else if(!!document.all){
if(!!window.atob){ie = 10;}
else if(!!document.addEventListener) {ie = 9;}
else if(!!document.querySelector){ie = 8;}
else if(!!window.XMLHttpRequest){ie = 7;}
else if(!!document.compatMode){ie = 6;}
else ie = 5;
}
}
}