@zerodep/is-promise

A simple, performant utility to determine if a value is a pending, resolved or rejected Promise.

Full documentation is available at the zerodep.app page.

Signature

declare const isPromise: (value: unknown) => boolean;

Examples

All @zerodep packages support both ESM and CJS formats, each complete with Typescript typings.

// ESM
import { isPromise } from '@zerodep/is-promise';

// CJS
const { isPromise } = require('@zerodep/is-promise');

// Arrays
isPromise([]); // false
isPromise([1, 2, 3]); // false
isPromise(['a', 'b', 'c']); // false

// BigInts
isPromise(42n); // false
isPromise(0n); // false
isPromise(-0n); // false
isPromise(-42n); // false

// Booleans
isPromise(true); // false
isPromise(false); // false

// Class
isPromise(
  class SomeClass {
    constructor() {}
  }
); // false

// Dates
isPromise(new Date()); // false
isPromise(new Date('1970-01-01T12:00:00.000Z')); // false
isPromise(new Date('2099-12-31')); // false

// Empty
isPromise(null); // false
isPromise(undefined); // false

// Errors
isPromise(new Error('message')); // false
isPromise(new AggregateError([new Error('err1'), new Error('err2')], 'message')); // false

// Floats
isPromise(3.14); // false
isPromise(0.0); // false
isPromise(-0.0); // false
isPromise(-3.14); // false
isPromise(Math.E); // false
isPromise(Math.PI); // false
isPromise(Number.MIN_VALUE); // false

// Functions
isPromise(() => 'function'); // false
isPromise(async () => 'function'); // false

// Generators
isPromise(function* () {
  yield 'a';
}); // false
isPromise(async function* () {
  yield 'a';
}); // false

// Maps
isPromise(new Map()); // false
isPromise(new Map([['key1', 123]])); // false
isPromise(new Map([['key1', 'value1']])); // false

// Numbers
isPromise(Number.POSITIVE_INFINITY); // false
isPromise(Number.MAX_SAFE_INTEGER); // false
isPromise(3e8); // false
isPromise(42); // false
isPromise(1); // false
isPromise(0); // false
isPromise(-0); // false
isPromise(-1); // false
isPromise(-42); // false
isPromise(-3e8); // false
isPromise(Number.MIN_SAFE_INTEGER); // false
isPromise(Number.NEGATIVE_INFINITY); // false
isPromise(Number.NaN); // false

// POJOs
isPromise({}); // false
isPromise({ key: 'string' }); // false
isPromise({ key: 123 }); // false

// Promise
isPromise(new Promise(() => {})); // true
isPromise(new Promise.all([])); // true
isPromise(new Promise.allSettled([])); // true
isPromise(new Promise.race([])); // true
isPromise(Promise.resolve()); // true

// Regular Expression
isPromise(/[regex]+/gi); // false
isPromise(new RegExp('d', 'gi')); // false

// Sets
isPromise(new Set()); // false
isPromise(new Set([1, 2, 3])); // false
isPromise(new Set(['a', 'b', 'c'])); // false

// Strings
isPromise(''); // false
isPromise('a longer string'); // false
isPromise('1000n'); // false
isPromise('3e8'); // false
isPromise('42'); // false
isPromise('3.14'); // false
isPromise('0'); // false
isPromise('-0'); // false
isPromise('-3.14'); // false
isPromise('-42'); // false
isPromise('-3e8'); // false
isPromise('-1000n'); // false

// Symbols
isPromise(Symbol()); // false
isPromise(Symbol('name')); // false

// This
isPromise(this); // false
isPromise(globalThis); // false

// TypedArrays
isPromise(new Int8Array(2)); // false
isPromise(new Int16Array(2)); // false
isPromise(new Int32Array(2)); // false
isPromise(new Uint8Array(2)); // false
isPromise(new Uint16Array(2)); // false
isPromise(new Uint32Array(2)); // false
isPromise(new Uint8ClampedArray(2)); // false

isPromise(new BigInt64Array(2)); // false
isPromise(new BigUint64Array(2)); // false

isPromise(new Float32Array(2)); // false
isPromise(new Float64Array(2)); // false

isPromise(new SharedArrayBuffer(512)); // false

// WeakMap and WeakSet
isPromise(new WeakMap()); // false
isPromise(new WeakSet()); // false

Negative Response

isPromise(['a', 'b', 'c']); // false
isPromise(1000n); // false
isPromise(true); // false
isPromise(new Date()); // false
isPromise(''); // false
isPromise(new Error('message')); // false
isPromise(3.14); // false
isPromise(() => 'function'); // false
isPromise(42); // false
isPromise(
  new Map([
    ['a', 1],
    ['b', 2],
  ])
); // false
isPromise(null); // false
isPromise({ an: 'object' }); // false
isPromise(/[regex]+/gi); // false
isPromise(new Set([1, 2, 3])); // false
isPromise('a string'); // false
isPromise(Symbol()); // false
isPromise(new Int32Array(2)); // false
isPromise(undefined); // false

ZeroDep Advantages

• Zero npm dependencies - completely eliminates all risk of supply-chain attacks, decreases node_modules folder size
• ESM & CJS - has both ecmascript modules and common javascript exports
• Tree Shakable - built to be fully tree shakable ensuring your packages are the smallest possible size
• Fully typed - typescript definitions are provided for every package for a better developer experience
• Semantically named - package and method names are easy to grok, remember, use, and read
• Documented - actually useful documentation with examples at zerodep.app
• Intelligently Packaged - multiple npm packages of different sizes available allowing a menu or a-la-carte composition of capabilities
• 100% Tested - all methods and packages are fully unit tested
• Predictably Versioned - semantically versioned for peace-of-mind upgrading, this includes changelogs
• MIT Licensed - permissively licensed for maximum usability