Promises & Generics

Generic Promise Helper

function wrap<T>(value: T): Promise<T> {
  return Promise.resolve(value);
}

wrap(5).then(n => console.log(n * 2)); // 10

Promise.allSettled

Returns a uniform shape regardless of fulfillment or rejection.

const results = await Promise.allSettled([
  fetch('/a'),
  fetch('/b'),
]);

results is typed as PromiseSettledResult<Response>[].

Creating a typed delayed function

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