creation

`Promise.resolve`

Returns a promise fulfilled with the given value, or — if the value is already a promise or thenable — the same/adopted promise. Handy for normalizing 'might be a promise' inputs.

Syntax

Promise.resolve(value)

Parameters

Parameter	Purpose
value	Any value — plain or thenable
thenable adoption	If value is a thenable, Promise.resolve follows its state
same-promise	If value is already a native Promise, the same instance is returned

Examples

const p = Promise.resolve(42);
p.then(v => console.log(v)); // 42

Immediately fulfilled with 42.

function loadCached(key) {
  return cache.has(key)
    ? Promise.resolve(cache.get(key))
    : fetch(key).then(r => r.json());
}

Return a resolved promise to keep the API async-uniform.

const inner = new Promise(res => setTimeout(() => res('x'), 100));
const outer = Promise.resolve(inner);
console.log(outer === inner); // true (adopts, doesn't wrap)

Passing a native promise returns the same instance.

Gotcha

Promise.resolve(thenable) follows the thenable — if that thenable rejects, so does yours. Cannot cancel or replace the value once created.

Promise.reject

Returns a promise that is already rejected with the given reason. Useful for early-exit paths in functions that must always return a promise.

new Promise

Constructs a promise from an executor function that receives resolve and reject callbacks. Use it to adapt callback-based or event-based APIs into promises.

Promise.withResolvers

Creates a promise and exposes its resolve and reject callbacks alongside it, avoiding the need to capture them from a new Promise executor. Added in ES2024 for the 'deferred' pattern.

← All JS Promise reference · async/await vs promises vs callbacks

Parameters

Examples

Gotcha

Related