9. Promises and async/await

// Promise states: pending → fulfilled | rejected (settled once)
function delay(ms) { return new Promise(resolve => setTimeout(resolve, ms)); }

fetch("/api/orders/1")
  .then(r => { if (!r.ok) throw new Error(`HTTP ${r.status}`); return r.json(); })
  .then(order => console.log(order))
  .catch(err => console.error(err))
  .finally(() => hideSpinner());

async function loadDashboard(userId) {
  try {
    const [user, orders] = await Promise.all([            // run in parallel
      fetch(`/api/users/${userId}`).then(r => r.json()),
      fetch(`/api/orders?user=${userId}`).then(r => r.json()),
    ]);
    return { user, orders };
  } catch (err) {
    console.error("Dashboard failed", err);
    throw err;
  }
}

// Timeout / cancellation with AbortController
const controller = new AbortController();
setTimeout(() => controller.abort(), 5000);
const res = await fetch("/api/report", { signal: controller.signal });   // or AbortSignal.timeout(5000)