function updateLights(state) { document.getElementById("red").classList.toggle("red", state === "red"); document.getElementById("green").classList.toggle("green", state === "green"); } function fetchStatus() { fetch("/status") .then(response => response.json()) .then(data => updateLights(data.state)) .catch(console.error); } function toggleLight() { fetch("/toggle", { method: "POST" }) .then(response => response.json()) .then(data => updateLights(data.state)) .catch(console.error); } setInterval(fetchStatus, 1000);