Can a promise change state after settling in JavaScript?

Pending (initial, waiting for the operation to complete), fulfilled (operation succeeded, resolve was called), and rejected (operation failed, reject was called). A promise transitions from pending to fulfilled or rejected once.

Use Promise.resolve(value) for an already-fulfilled promise. Use Promise.reject(reason) for an already-rejected promise. These are settled immediately. .then/.catch still run (as microtasks).

No. There is no promise.state property. You can only react to settlement via .then, .catch, and .finally. If you need to track state, do it yourself by attaching .then and .catch handlers that update a variable.