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deferred.ts
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deferred.ts
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// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
// 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> {
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:
*
* const p = deferred<number>();
* // ...
* p.resolve(42);
*/
export function deferred<T>(): Deferred<T> {
let methods;
const promise = new Promise<T>((resolve, reject): void => {
methods = { resolve, reject };
});
return Object.assign(promise, methods) as Deferred<T>;
}