代碼在ext里的src/core/ext.js下
最新的ext3.0beat1的代碼如下：
ua = navigator.userAgent.toLowerCase(),
check = function(r){
return r.test(ua);
},
isStrict = document.compatMode == "CSS1Compat",
isOpera = check(/opera/),
isChrome = check(/chrome/),
isWebKit = check(/webkit/),
isSafari = !isChrome && check(/safari/),
isSafari3 = isSafari && check(/version//3/),
isSafari4 = isSafari && check(/version//4/),
isIE = !isOpera && check(/msie/),
isIE7 = isIE && check(/msie 7/),
isIE8 = isIE && check(/msie 8/),
isGecko = !isWebKit && check(/gecko/),
isGecko3 = isGecko && check(/rv:1/.9/),
isBorderBox = isIE && !isStrict,
isWindows = check(/windows|win32/),
isMac = check(/macintosh|mac os x/),
isAir = check(/adobeair/),
isLinux = check(/linux/),
isSecure = /^https/i.test(window.location.protocol);
而2.2.1下（在source/core/ext.js里）的為
var ua = navigator.userAgent.toLowerCase();
var isStrict = document.compatMode == "CSS1Compat",
isOpera = ua.indexOf("opera") > -1,
isChrome = ua.indexOf("chrome") > -1,
isSafari = !isChrome && (/webkit|khtml/).test(ua),
isSafari3 = isSafari && ua.indexOf('webkit/5') != -1,
isIE = !isOpera && ua.indexOf("msie") > -1,
isIE7 = !isOpera && ua.indexOf("msie 7") > -1,
isIE8 = !isOpera && ua.indexOf("msie 8") > -1,
isGecko = !isSafari && !isChrome && ua.indexOf("gecko") > -1,
isGecko3 = isGecko && ua.indexOf("rv:1.9") > -1,
isBorderBox = isIE && !isStrict,
isWindows = (ua.indexOf("windows") != -1 || ua.indexOf("win32") != -1),
isMac = (ua.indexOf("macintosh") != -1 || ua.indexOf("mac os x") != -1),
isAir = (ua.indexOf("adobeair") != -1),
isLinux = (ua.indexOf("linux") != -1),
isSecure = window.location.href.toLowerCase().indexOf("https") === 0;
