Detect the current browser and version using the user agent.

browserdetect.js

/**
 *  browserdetect.js
 *  Detect the current browser and version using the user agent.
 *  Credit: https://stackoverflow.com/a/13480430/6272119
 */
var BrowserDetect = {
    dataBrowser: [
        { string: navigator.userAgent, subString: "Edge", identity: "MS Edge" },
        { string: navigator.userAgent, subString: "MSIE", identity: "Explorer" },
        { string: navigator.userAgent, subString: "Trident", identity: "Explorer" },
        { string: navigator.userAgent, subString: "Firefox", identity: "Firefox" },
        { string: navigator.userAgent, subString: "Opera", identity: "Opera" },
        { string: navigator.userAgent, subString: "OPR", identity: "Opera" },
        { string: navigator.userAgent, subString: "Chrome", identity: "Chrome" },
        { string: navigator.userAgent, subString: "Safari", identity: "Safari" }
    ],

    init: function() {
        this.browser = this.searchString(this.dataBrowser) || "Other";
        this.version = this.searchVersion(navigator.userAgent) || this.searchVersion(navigator.appVersion) || "Unknown";
    },

    searchString: function(data) {
        for (var i = 0; i < data.length; i++) {
            var dataString = data[i].string;
            this.versionSearchString = data[i].subString;

            if (dataString.indexOf(data[i].subString) !== -1) {
                return data[i].identity;
            }
        }
    },

    searchVersion: function(dataString) {
        var index = dataString.indexOf(this.versionSearchString);

        if (index === -1) {
            return;
        }

        var rv = dataString.indexOf("rv:");
        if (this.versionSearchString === "Trident" && rv !== -1) {
            return parseFloat(dataString.substring(rv + 3));
        } else {
            return parseFloat(dataString.substring(index + this.versionSearchString.length + 1));
        }
    }
};

BrowserDetect.init();

modernizr-browser-tests.js

// Add browser tests
var browser_tests = {
    'chrome':   function() { return BrowserDetect.browser  == 'Chrome';                                                           },
    'firefox':  function() { return BrowserDetect.browser  == 'Firefox';                                                          },
    'safari':   function() { return BrowserDetect.browser  == 'Safari';                                                           },
    'edge':     function() { return BrowserDetect.browser  == 'MS Edge';                                                          },
    'ie':       function() { return BrowserDetect.browser  == 'Explorer';                                                         },
    'ie11':     function() { return (BrowserDetect.browser == 'Explorer' && BrowserDetect.version == 11);                         },
    'lt-ie11':  function() { return (BrowserDetect.browser == 'Explorer' && BrowserDetect.version < 11);                          },
    'gt-ie10':  function() { return (BrowserDetect.browser == 'Explorer' && BrowserDetect.version > 10);                          },
    'ie10':     function() { return (BrowserDetect.browser == 'Explorer' && BrowserDetect.version == 10);                         },
    'lt-ie10':  function() { return (BrowserDetect.browser == 'Explorer' && BrowserDetect.version < 10);                          },
    'gt-ie9':   function() { return (BrowserDetect.browser == 'Explorer' && BrowserDetect.version > 9);                           },
    'ie9':      function() { return (BrowserDetect.browser == 'Explorer' && BrowserDetect.version == 9);                          },
    'lt-ie9':   function() { return (BrowserDetect.browser == 'Explorer' && BrowserDetect.version < 9);                           },
    'mobile':   function() { return (/Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent)); }
}
Modernizr.addTest(browser_tests);