js判定浏览器的种类

<script type="text/javascript">              
    function userAgent(){                 
     var ua = navigator.userAgent;                  
     ua = ua.toLowerCase();                  
     var match = /(webkit)[ \/]([\w.]+)/.exec(ua) ||                  
     /(opera)(?:.*version)?[ \/]([\w.]+)/.exec(ua) ||                  
     /(msie) ([\w.]+)/.exec(ua) ||                  
     !/compatible/.test(ua) && /(mozilla)(?:.*? rv:([\w.]+))?/.exec(ua) ||
     [];      //如果需要获取浏览器版本号：match[2]
     alert(match);
     switch (match[1]) {      
      case "msie":      //ie      
       if (parseInt(match[2]) === 6)    //ie6       
        document.body.innerHTML='IE6 '       
        else if (parseInt(match[2]) === 7)    //ie7
            alert("ie7");       
        else if (parseInt(match[2]) === 8)    //ie8
            alert("ie8"); break;  
        case "webkit":     //safari or chrome
            alert("safari or chrome"); break;      
         case "opera":      //opera
             alert("opera"); break; 
        case "mozilla":    //Firefox
        alert("Firefox"); break; default: break;
} 
}     
        userAgent();   
    </script>