Async/Await with Types

Async Functions

async function delay(ms: number): Promise<void> {
  return new Promise(resolve => setTimeout(resolve, ms));
}

async function fetchData(): Promise<string> {
  await delay(500);
  return "done";
}

Return Types

function getNumber(): Promise<number> { /* … */ }

If you forget to await, the function returns a Promise<...> which may cause type mismatches.

Error Handling

async function safeFetch(url: string): Promise<string | null> {
  try {
    const r = await fetch(url);
    if (!r.ok) throw new Error(r.statusText);
    return await r.text();
  } catch (e) {
    console.error(e);
    return null;
  }
}

Parallel Await with Promise.all

async function loadAll(urls: string[]): Promise<string[]> {
  const promises = urls.map(u => fetch(u).then(r => r.text());
  return Promise.all(promises);
}