判断当前浏览器类型代码

<script type="text/javascript" >
<!--
function getOs()
{
if(isIE = navigator.userAgent.indexOf("MSIE")!=-1)
{
return "MSIE";
}
if(isFirefox=navigator.userAgent.indexOf("Firefox")!=-1)
{
        return "Firefox";
}
if(isChrome=navigator.userAgent.indexOf("Chrome")!=-1)
{
return "Chrome";
}
if(isSafari=navigator.userAgent.indexOf("Safari")!=-1)
{
return "Safari";
} 
if(isOpera=navigator.userAgent.indexOf("Opera")!=-1)
{
return "Opera";
}
}
alert("type -> "+getOs());
-->
</script>