@nkp/is-promise

Utility functions for determining if values conform to the Promise or PromiseLike interfaces.

// interface

/**
 * Does the unknown value conform to the Promise interface?
 *
 * @param value   any value
 * @returns       whether the value is Promise
 */
declare function isPromise<T>(value: PromiseLike<T> | unknown): value is Promise<T>;

/**
 * Does the unknown value conform to the PromiseLike interface?
 *
 * @param value   any value
 * @returns       whether the value is a PromiseLike
 */
declare function isPromiseLike<T>(value: PromiseLike<T> | unknown): value is PromiseLike<T>;

/**
 * Does the PromiseLike value conform to the Promise interface?
 *
 * @param like    PromiseLike value
 * @returns       whether the value is a Promise
 */
declare function andIsPromise<T>(like: PromiseLike<T>): like is Promise<T>;

// usage

import { isPromise, isPromiseLike, andIsPromise, } from '@nkp/is-promise';

// isPromiseLike
console.log(isPromiseLike(new Promise<void>((res) => res())));      // true
console.log(isPromiseLike(Promise.reject()));                       // true
console.log(isPromiseLike(Promise.resolve().catch(() => {})));      // true
console.log(isPromiseLike({ then() {}, catch() {}, }));             // true
console.log(isPromiseLike({ then: () => {}, catch: () => {}, }));   // true
console.log(isPromiseLike({ then: () => {}, }));                    // true
console.log(isPromiseLike({ catch: () => {}, }));                   // false

// isPromise
console.log(isPromise(new Promise<void>((res) => res())));      // true
console.log(isPromise(Promise.resolve()));                      // true
console.log(isPromise(Promise.reject().catch(() => {})));       // true
console.log(isPromise({ then() {}, catch() {}, }));             // true
console.log(isPromise({ then: () => {}, catch: () => {}, }));   // true
console.log(isPromise({ then: () => {}, }));                    // false
console.log(isPromise({ catch: () => {}, }));                   // false

// andIsPromise
// takes a PromiseLike value and determines if it is actually a promise

Table of contents

• Installation
  • npm
  • yarn
  • pnpm
• Publishing

Installation

npm

npm install @nkp/is-promise

yarn

yarn add @nkp/is-promise

pnpm

pnpm add @nkp/is-promise

Publishing

To a release a new version:

1. Update the version number in package.json
2. Push the new version to the master branch on GitHub
3. Create a new release on GitHub for the latest version

This will trigger a GitHub action that tests and publishes the npm package.