Create a Promise whose `resolve` and `reject` are exposed externally. Useful when you need to settle a promise from outside its executor — e.g. waiting on an event-driven response.
TypeScript
type Deferred<T> = {
promise: Promise<T>;
resolve: (value: T | PromiseLike<T>) => void;
reject: (reason?: unknown) => void;
};
export function deferred<T>(): Deferred<T> {
let resolve!: Deferred<T>['resolve'];
let reject!: Deferred<T>['reject'];
const promise = new Promise<T>((res, rej) => { resolve = res; reject = rej; });
return { promise, resolve, reject };
}
// Wait for a one-shot event
const d = deferred<MessageEvent>();
worker.addEventListener('message', d.resolve, { once: true });
const msg = await d.promise;Save your own code snippets
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