Javascript 判断浏览器

                var Sys = {};
                var ua = navigator.userAgent.toLowerCase();
                if (window.ActiveXObject)//IE
                    Sys.ie = ua.match(/msie ([\d.]+)/)[1]
                else if (document.getBoxObjectFor)//Firefox
                    Sys.firefox = ua.match(/firefox\/([\d.]+)/)[1]
                else if (window.MessageEvent && !document.getBoxObjectFor)//Chrome
                    Sys.chrome = ua.match(/chrome\/([\d.]+)/)[1]
                else if (window.opera)//Opera
                    Sys.opera = ua.match(/opera.([\d.]+)/)[1]
                else if (window.openDatabase)//Safari
                    Sys.safari = ua.match(/version\/([\d.]+)/)[1];
                //以下进行测试
                if (Sys.ie) alert('IE: ' + Sys.ie);//Sys.ie是版本号
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