detect IE and version number through injected conditional comments.js

//EnhanceJS isIE test idea

//detect IE and version number through injected conditional comments (no UA detect, no need for cond. compilation / jscript check)

//version arg is for IE version (optional)
//comparison arg supports 'lte', 'gte', etc (optional)

var isIE = (function(){
  
  var doc = document,
    doc_elem = doc.documentElement,
    cache = {},
    elem;
  
  return function( version, comparison ) {
    var key = [ comparison || '', 'IE', version || '' ].join(' ');
    
    if ( cache[ key ] === undefined ) {
      elem = elem || doc.createElement( 'B' );
      elem.innerHTML = '<!--[if '+ key +']><b id="iecctest"></b><![endif]-->';
      doc_elem.appendChild( elem );
      cache[ key ] = !!doc.getElementById( 'iecctest' );
      doc_elem.removeChild( elem );
    }
    
    return cache[ key ];
  };
  
})();

// minified:
var isIE=(function(){var e=document,d=e.documentElement,a={},c;return function b(f,h){var g=[h||"","IE",f||""].join(" ");if(a[g]===undefined){c=c||e.createElement("B");c.innerHTML="<!--[if "+g+']><b id="iecctest"></b><![endif]-->';d.appendChild(c);a[g]=!!e.getElementById("iecctest");d.removeChild(c)}return a[g]}})();

// See http://jsfiddle.net/cowboy/75GBD/
		
//is it IE?		
isIE(); 

//is it IE6?
isIE(6);

//is it less than or equal to IE 6?
isIE(7,'lte');

Benefits:

• results are memoized
• only a single dom element is created