JSFiddle - React, Tailwind, and code Playground

JavaScript

var os = (function () {
    var ua = navigator.userAgent.toLowerCase();
    return {
        isWindows: /(windows|win95|win32|win64)/.test(ua),
        isLinuxUNIX: /(linux|freebsd|ssl-mm|netpositive|sunos|w3m|irixx11)/.test(ua),
        isApple: /(mac os|mac_powerpc)/.test(ua)
    };
}());

if (os.isWindows) {
    /* do stuff... */
    alert("You're using Windows.");
}
if (os.isLinuxUNIX) {
    alert("You're using Linux or UNIX.");
}
if (os.isApple) {
    alert("You're using Apple.");
}