std@0.139.0/async/deferred.ts

Deno standard library
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deferred.ts
// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
// TODO(ry) It'd be better to make Deferred a class that inherits from// Promise, rather than an interface. This is possible in ES2016, however// typescript produces broken code when targeting ES5 code.// See https://github.com/Microsoft/TypeScript/issues/15202// At the time of writing, the github issue is closed but the problem remains.export interface Deferred<T> extends Promise<T> { readonly state: "pending" | "fulfilled" | "rejected"; resolve(value?: T | PromiseLike<T>): void; // deno-lint-ignore no-explicit-any reject(reason?: any): void;}
/** Creates a Promise with the `reject` and `resolve` functions * placed as methods on the promise object itself. It allows you to do: * * ```ts * import { deferred } from "./deferred.ts"; * * const p = deferred<number>(); * // ... * p.resolve(42); * ``` */export function deferred<T>(): Deferred<T> { let methods; let state = "pending"; const promise = new Promise<T>((resolve, reject): void => { methods = { async resolve(value: T | PromiseLike<T>) { await value; state = "fulfilled"; resolve(value); }, // deno-lint-ignore no-explicit-any reject(reason?: any) { state = "rejected"; reject(reason); }, }; }); Object.defineProperty(promise, "state", { get: () => state }); return Object.assign(promise, methods) as Deferred<T>;}