#async

TypeScriptintermediate

Awaited<T> and unwrapping nested promise types

type Nested = Promise<Promise<Promise<string>>>;
type Flat = Awaited<Nested>;

export async function loadUser(): Promise<{ id: string; name: string }> {
  return { id: "1", name: "Ada" };

Unwrap Promise<Promise<Promise<T>>> down to T in one step, the way await does at runtime, using TypeScript's built-in recursive helper.

Web Platformadvanced

A tiny promise-based wrapper around IndexedDB

const dbPromise = new Promise<IDBDatabase>((resolve, reject) => {
  const request = indexedDB.open("app-cache", 1);
  request.onupgradeneeded = () => request.result.createObjectStore("kv");
  request.onsuccess = () => resolve(request.result);
  request.onerror = () => reject(request.error);

Turn IndexedDB's callback-and-event API into two functions, idbGet and idbSet, that behave like a normal async key-value store.