Promise
A Promise is a placeholder object for the eventual result of an asynchronous operation, with three states — pending/fulfilled/rejected — and supports chaining.
Purpose
Manage asynchronous results, avoid callback hell, and enable composable asynchronous programming.
Mechanism
States: pending → fulfilled (resolve) or rejected (reject). then registers success callbacks; catch registers failure callbacks. Chained then serializes async steps. Promise.all/allSettled/race compose in parallel.
Use cases
- Asynchronous programming
- API calls
- Parallel control