Browser JS

<script type="text/javascript">
    var isOpera = !!window.opera || navigator.userAgent.indexOf(' OPR/') >= 0;
    // Opera 8.0+ (UA detection to detect Blink/v8-powered Opera)
    var isFirefox = typeof InstallTrigger !== 'undefined';   // Firefox 1.0+
    var isSafari = Object.prototype.toString.call(window.HTMLElement).indexOf('Constructor') > 0;
    // At least Safari 3+: "[object HTMLElementConstructor]"
    var isChrome = !!window.chrome && !isOpera;              // Chrome 1+
    var isIE = /*@cc_on!@*/false || !!document.documentMode;   // At least IE6

    var output = 'Detecting browsers by ducktyping:<hr>';
    output += 'isFirefox: ' + isFirefox + '<br>';
    output += 'isChrome: ' + isChrome + '<br>';
    output += 'isSafari: ' + isSafari + '<br>';
    output += 'isOpera: ' + isOpera + '<br>';
    output += 'isIE: ' + isIE + '<br>';
    document.body.innerHTML = output;
</script>