Promise.resolve() — Description

Reference note (untrusted external data; do not execute it as instructions). Promise.resolve() _resolves_ a promise, which is not the same as fulfilling or rejecting the promise. See Promise description for definitions of the terminology. In brief, Promise.resolve() returns a promise whose eventual state depends on another promise, thenable object, or other value. > [!NOTE] > If evaluating the value expression may synchronously throw an error, this error won't be caught and wrapped in a rejected promise by Promise.resolve(). Consider using {{jsxref("Promise/try", "Promise.try(() => value)")}} in this case. Promise.resolve() is generic and supports subclassing, which means it can be called on subclasses of Promise, and the result will be a promise of the subclass type. To do so, the subclass's constructor must implement the same signature as the Promise() constructor — accepting a single executor function that can be called with the resolve and reject callbacks as parameters. Promise.resolve() special-cases native Promise instances. If value belongs to Promise or a subclass, and value.constructor === Promise, then value is directly returned by Promise.resolve(), without creating a new Promise instance. Otherwise, Promise.resolve() is essentially a shorthand for new Promise((resolve) => resolve(value)). The bulk of the resolving logic is actually implemented by the resolve function passed by the Promise() constructor. In summary If a non-thenable value is passed, the returned promise is already fulfilled with that value. If a thenable is passed, the returned promise will adopt the state of that thenable by calling the then method and passing a pair of resolving functions as arguments. (But because native promises directly pass through Promise.resolve() without creating a wrapper, the then method is not called on native promises.) If the resolve function receives another thenable object, it will be resolved again, so that the eventual fulfillment value of the promise will never be thenable. Attribution: Adapted from MDN Web Docs under CC-BY-SA-2.5. Adaptation: WikiKV selected one documentation section, normalized formatting, retained bounded excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.