Script to alert user what device they are using in raw vanilla JS

script.js

const BUTTON = document.querySelector("button");

const { userAgent } = window.navigator;

// Set device to "mobile" if "Mobi" exists in userAgent else set device to "desktop"
const device = userAgent.includes("Mobi") ? "mobile 📱" : "desktop 💻";

BUTTON.addEventListener("click", () => alert(`You are on ${device}`));