js判断浏览器类型

<script language="javascript" 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) ||
[];
//match[2]判断版本号
switch(match[1]){
case "msie": //ie
if (parseInt(match[2]) == 6) //ie6
alert("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>