JavaScript判断浏览器的类型和版本

<script type="text/javascript">
        var Sys = {};
        var ua = navigator.userAgent.toLowerCase();
        if (window.ActiveXObject)
            Sys.ie = ua.match(/msie ([/d.]+)/)[1]
        else if (document.getBoxObjectFor)
            Sys.firefox = ua.match(/firefox//([/d.]+)/)[1]
        else if (window.MessageEvent && !document.getBoxObjectFor)
            Sys.chrome = ua.match(/chrome//([/d.]+)/)[1]
        else if (window.opera)
            Sys.opera = ua.match(/opera.([/d.]+)/)[1]
        else if (window.openDatabase)
            Sys.safari = ua.match(/version//([/d.]+)/)[1];
       
        //以下进行测试
        if(Sys.ie) document.write('IE: '+Sys.ie);
        if(Sys.firefox) document.write('Firefox: '+Sys.firefox);
        if(Sys.chrome) document.write('Chrome: '+Sys.chrome);
        if(Sys.opera) document.write('Opera: '+Sys.opera);
        if(Sys.safari) document.write('Safari: '+Sys.safari);

    </script>