Opera
var isOpera = (!!window.opr && !!opr.addons) || !!window.opera || navigator.userAgent.indexOf(' OPR/') >= 0;
Firefox 1.0+
var isFirefox = typeof InstallTrigger !== 'undefined';
At least Safari 3+: “[object HTMLElementConstructor]”
var isSafari = Object.prototype.toString.call(window.HTMLElement).indexOf('Constructor') > 0;
Internet Explorer 6-11
var isIE = /*@cc_on!@*/false || !!document.documentMode;
Edge 20+
var isEdge = !isIE && !!window.StyleMedia;
Chrome 1+
var isChrome = !!window.chrome && !!window.chrome.webstore;