js检测浏览器版本代码，兼容ie11

原文：http://blog.csdn.net/tenkin/article/details/11640165

<script type="text/javascript">
                var userAgent = navigator.userAgent, 
                rMsie = /(msies|trident.*rv:)([w.]+)/, 
                rFirefox = /(firefox)/([w.]+)/, 
                rOpera = /(opera).+version/([w.]+)/, 
                rChrome = /(chrome)/([w.]+)/, 
                rSafari = /version/([w.]+).*(safari)/;
                var browser;
                var version;
                var ua = userAgent.toLowerCase();
                function uaMatch(ua) {
                    var match = rMsie.exec(ua);
                    if (match != null) {
                        return { browser : "IE", version : match[2] || "0" };
                    }
                    var match = rFirefox.exec(ua);
                    if (match != null) {
                        return { browser : match[1] || "", version : match[2] || "0" };
                    }
                    var match = rOpera.exec(ua);
                    if (match != null) {
                        return { browser : match[1] || "", version : match[2] || "0" };
                    }
                    var match = rChrome.exec(ua);
                    if (match != null) {
                        return { browser : match[1] || "", version : match[2] || "0" };
                    }
                    var match = rSafari.exec(ua);
                    if (match != null) {
                        return { browser : match[2] || "", version : match[1] || "0" };
                    }
                    if (match != null) {
                        return { browser : "", version : "0" };
                    }
                }
                var browserMatch = uaMatch(userAgent.toLowerCase());
                if (browserMatch.browser) {
                    browser = browserMatch.browser;
                    version = browserMatch.version;
                }
                document.write(browser+version);        
                    </script>