javascript: detect browser type by features detection

BROWSERS-DETECT.js

// IE
// conditional comment
(function(dom){
    dom.innerHTML = '<!--[if IE]><br><![endif]-->';
    return !!dom.firstChild.tagName;
})(document.createElement('p'));


// Conditional Compilation 
// http://msdn.microsoft.com/en-us/library/ahx1z4fs(VS.80).aspx
IE=/*@cc_on!@*/!1;
IE55=/*@cc_on@if(@_jscript_version==5.5)!@end@*/!1;
IE6=/*@cc_on@if(@_jscript_version==5.6)!@end@*/!1;
IE7=/*@cc_on@if(@_jscript_version==5.7)!@end@*/!1;
IE8=/*@cc_on@if(@_jscript_version==5.8)!@end@*/!1;

// IE < 9
// Array bug
!-[1, ];
!','.split(/,/).length;
// no support of vertical tab character '\v'
!+'\v1'
!-'\v1'
'\v' == 'v'

// IE8
!!win.XDomainRequest

/********************************************************************************/

// FireFox
!!document.getBoxObjectFor || 'mozInnerScreenX' in window;

// FireFox 1.5
'some' in Array;

// FireFox 2.0
(function x(){})[-6]=='x'
// !!window.globalStorage;

// FireFox 3.0
(function x(){})[-5]=='x';
// !!window.MessageEvent;
// 'reduce' in Array

// FireFox 2.0 / 3.0
/a/[-1]=='a';

// FireFox 3.5
!!Object.getPrototypeOf;

// FireFox 3.6
'mozInnerScreenX' in window;  // alt: !!document.body.mozMatchesSelector

// FireFox < 4 (Gecko < 2)
(function(o) { o[o] = o+""; return o[o] != o+""; })(new String("__count__"));

/********************************************************************************/

// Opera
!!window.opera && !!window.opera.toString().indexOf('Opera');

// Opera 9
/^function \(/.test([].sort);

/********************************************************************************/

// Safari
/a/.__proto__ == '//';

/********************************************************************************/

// chrome
/source/.test(/a/.toString+'');

/********************************************************************************/

// webkit
!!window.devicePixelRatio;

// http://www.thespanner.co.uk/2009/01/29/detecting-browsers-javascript-hacks/