src/browser-detector.js

"use strict";

var detector = module.exports = {};

detector.isIE = function(version) {
    function isAnyIeVersion() {
        var agent = navigator.userAgent.toLowerCase();
        return agent.indexOf("msie") !== -1 || agent.indexOf("trident") !== -1 || agent.indexOf(" edge/") !== -1;
    }

    if(!isAnyIeVersion()) {
        return false;
    }

    if(!version) {
        return true;
    }

    //Shamelessly stolen from https://gist.github.com/padolsey/527683
    var ieVersion = (function(){
        var undef,
            v = 3,
            div = document.createElement("div"),
            all = div.getElementsByTagName("i");

        do {
            div.innerHTML = "<!--[if gt IE " + (++v) + "]><i></i><![endif]-->";
        }
        while (all[0]);

        return v > 4 ? v : undef;
    }());

    return version === ieVersion;
};

detector.isLegacyOpera = function() {
    return !!window.opera;
};