function getBrowser() {
    var Sys = {};
    var ua = navigator.userAgent.toLowerCase();
    var s;
    (s = ua.match(/msie ([\d.]+)/)) ? Sys.ie = s[1] :
                (s = ua.match(/firefox\/([\d.]+)/)) ? Sys.firefox = s[1] :
                (s = ua.match(/chrome\/([\d.]+)/)) ? Sys.chrome = s[1] :
                (s = ua.match(/opera.([\d.]+)/)) ? Sys.opera = s[1] :
                (s = ua.match(/version\/([\d.]+).*safari/)) ? Sys.safari = s[1] : 0;
    if (Sys.ie) return "IE";
    else if (Sys.firefox) return "Firefox";
    else if (Sys.chrome) return "Chrome";
    else if (Sys.opera) return "Opera";
    else if (Sys.safari) return "Safari";
}

js 判断浏览器的类型