判断浏览器版本

　　　　 var idSeed = 0,
        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);