Browser detection with Javascript

browserCheck.js

var BROWSERS = {
    chrome: {
        name: "Google Chrome or Chromium",
        codes: {
            chrome: "Chrome"
        },
        supportVersion: 0
    },
    firefox: {
        name: "Mozilla Firefox",
        codes: {
            firefox: "Firefox"
        },
        supportVersion: 0
    },
    edge: {
        name: "Microsoft Edge",
        codes: {
            edge: "Edge"
        },
        supportVersion: 0
    },
    internetExplorer: {
        name: "Microsoft Internet Explorer",
        codes: {
            trident: "Trident",
            msie: "MSIE"
        },
        supportVersion: 10
    },
    opera: {
        name: "Opera",
        codes: {
            opera: "Opera",
            opr: "OPR"
        },
        supportVersion: 0
    },
    safari: {
        name: "Apple Safari",
        codes: {
            safari: "Safari"
        },
        supportVersion: 0
    },
    unknown: {
        name: "unknown",
        code: ""
    }
};
var COMPATIBLE = "compatible";
var rv = "rv";

function getVersion(userAgent, browserCode, delimiterBefore, delimiterAfter) {
    var versionString = userAgent.substring(userAgent.indexOf(browserCode));
    var index = versionString.indexOf(delimiterBefore) + 1;
    return versionString.substring(index, versionString.indexOf(delimiterAfter) > -1 ? versionString.indexOf(delimiterAfter) : versionString.length);
}

(function () {
    var userAgent = window.navigator.userAgent;
    var browser = {
        name: '',
        version: '',
        compatibilityMode: false,
        compatibilityVersion: ''
    };
    console.log(userAgent);
    if (userAgent.indexOf(BROWSERS.firefox.codes.firefox) > -1) {
        // "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:61.0) Gecko/20100101 Firefox/61.0"
        browser.name = BROWSERS.firefox.name;
        browser.version = getVersion(userAgent, BROWSERS.firefox.codes.firefox, '/', ' ');
    } else if (userAgent.indexOf(BROWSERS.opera.codes.opera) > -1 || userAgent.indexOf(BROWSERS.opera.codes.opr) > -1) {
        browser.name = BROWSERS.opera.name;
        //"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36 OPR/57.0.3098.106"
        if (userAgent.indexOf(BROWSERS.opera.codes.opera) > -1) {
            browser.version = getVersion(userAgent, BROWSERS.opera.codes.opera, '/', ' ');;
        } else {
            browser.version = getVersion(userAgent, BROWSERS.opera.codes.opr, '/', ' ');;
        }
    } else if (userAgent.indexOf(BROWSERS.internetExplorer.codes.trident) > -1) {
        browser.name = BROWSERS.internetExplorer.name;
        // "Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; .NET4.0C; .NET4.0E; Zoom 3.6.0; wbx 1.0.0; rv:11.0) like Gecko"
        var version = getVersion(userAgent, BROWSERS.internetExplorer.codes.trident, '/', ';');
        if (version === '7.0') {
            browser.version = getVersion(userAgent, rv, ':', ')');
        } else {
            if (userAgent.indexOf(BROWSERS.internetExplorer.codes.msie) > -1) {
                browser.version = getVersion(userAgent, BROWSERS.internetExplorer.codes.msie, ' ', ';');
            }
        }
        /**
         * Check if browser running in compatibility mode (simulating an older version)
         */
        if (userAgent.indexOf(COMPATIBLE) > -1) {
            browser.compatibilityMode = true;
            browser.compatibilityVersion = getVersion(userAgent, BROWSERS.internetExplorer.codes.msie, ' ', ';');
        }
        /**
         * Custom message to user for older version of the application
         */
        if (browser.compatibilityMode) {
            alert('You are working with developer options turned ON and emulating a different device. Application might not work as expected.');
            if (Number(browser.compatibilityVersion) < BROWSERS.internetExplorer.supportVersion) {
                alert('You are working with developer options turned ON and emulating a different device with lower browser version. Application might not work as expected.');
            }
        } else if (Number(browser.version) < BROWSERS.internetExplorer.supportVersion) {
            alert('You are working in older browser version. Application might not work as expected.');
        }
    } else if (userAgent.indexOf(BROWSERS.edge.codes.edge) > -1) {
        // "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36 Edge/16.16299"
        browser.name = BROWSERS.edge.name;
        browser.version = getVersion(userAgent, BROWSERS.edge.codes.edge, '/', ' ');
    } else if (userAgent.indexOf(BROWSERS.chrome.codes.chrome) > -1) {
        browser.name = BROWSERS.chrome.name;
        // "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/66.0.3359.181 Chrome/66.0.3359.181 Safari/537.36"
        browser.version = getVersion(userAgent, BROWSERS.chrome.codes.chrome, '/', ' ');
    } else if (userAgent.indexOf(BROWSERS.safari.codes.safari) > -1) {
        browser.name = BROWSERS.safari.name;
        // "Mozilla/5.0 (iPhone; CPU iPhone OS 11_4 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/11.0 Mobile/15E148 Safari/604.1 980x1306"
        browser.version = getVersion(userAgent, BROWSERS.safari.codes.safari, '/', ' ');
    } else {
        browser.name = BROWSERS.unknown.name;
        browser.version = BROWSERS.unknown.code;
    }
    console.log(browser);
})();