Browser name and version in javascript

<script type="text/javascript">
alert(navigator);
var browserName=navigator.appName;  
var userAgent = navigator.userAgent
alert(browserName);
    if (browserName=="Microsoft Internet Explorer"){
        alert("Microsoft Internet Explorer");
        alert("Microsoft Internet Explorer Version : "+navigator.appVersion);
        alert(document.documentMode;);
     
    }
    else if (browserName=="Netscape" && userAgent.indexOf("Chrome") != -1 ){
        alert("Google Chrome");
        alert("Google Chrome Version: "+navigator.appVersion);
    }
    else if(browserName=="Netscape" && userAgent.indexOf("Mozilla") != -1){
        alert("Mozilla Firefox");
        alert("Mozilla Firefox Version : "+navigator.appVersion);
    }else{
        alert("Another browser");
    }
</script>