Chrome client latest (stable) version checker (https://jsbin.com/bihejimoko/edit?js,console)

isChromeLatestVersion.js

// Check whether client has latest (stable) version of Chrome

if (isChrome()) {
    getVersionInfo()
        .then((result) => {
            const output = 
                `Stable Version Info: Full (Major)\n` +
                `~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n` +
                `Client: ${result.clientVer} (${result.clientVerMajor})\n` +
                `Latest: ${result.latestVer} (${result.latestVerMajor})\n` +
                `Is client latest? - ${result.isLatest} (${result.isLatestMajor})`;
            console.log(output);
        });
} else {
    console.log("This ain't even Chrome!");
}


/**
 * Is current browser Chrome?
 * @returns {boolean}
 */
function isChrome() {
    const isChromium = window.chrome;
    const winNav = window.navigator;
    const vendorName = winNav.vendor;
    const isOpera = winNav.userAgent.indexOf("OPR") > -1;
    const isIEedge = winNav.userAgent.indexOf("Edge") > -1;

    return (
        isChromium !== null &&
        typeof isChromium !== "undefined" &&
        vendorName === "Google Inc." &&
        isOpera === false &&
        isIEedge === false
    );
}

/**
 * Get Chrome version info
 * @returns {Promise<Object>}
 */
function getVersionInfo() {
    const userAgent = window.navigator.userAgent;

    const clientVer = userAgent.match(/Chrom(e|ium)\/(([0-9]|\.)+)/)[2];
    const clientVerMajor = clientVer.slice(0, 2);

    let opSys = "";

    if (userAgent.indexOf("Linux") !== -1) opSys = "linux";
    if (userAgent.indexOf("Mac") !== -1) opSys = "mac";
    if (userAgent.indexOf("Windows") !== -1) opSys = "win";

    const fetchUrl = `https://omahaproxy.appspot.com/all.json?os=${opSys}&channel=stable`;

    return fetch(fetchUrl)
        .then((res) => res.json())
        .then((jsonResponse) => {
            const latestVer = jsonResponse[0].versions[0].current_version;
            const latestVerMajor = latestVer.slice(0, 2);

            return {
                clientVer,
                clientVerMajor,
                latestVer,
                latestVerMajor,
                isLatest: (clientVer === latestVer),
                isLatestMajor: (clientVerMajor === latestVerMajor),
            };
        });
}

Demo: https://jsbin.com/bihejimoko/edit?js,console