Promises Revisited

Promises provide a much cleaner and more manageable abstraction for asynchronous operations compared to callbacks. A `Promise` object acts as a placeholder for a future value. The key benefit of promises lies in their chainability. The `.then()` method itself returns a new promise, which allows you to chain multiple asynchronous steps together in a flat, readable sequence, effectively solving the 'callback hell' problem. Each `.then()` block receives the result of the previous promise in the chain. Error handling is also greatly improved. Instead of handling errors in each callback, you can add a single `.catch()` block at the end of the chain to handle any error that occurs in any of the preceding steps. This centralizes error logic and makes the code much cleaner. Another powerful feature is `Promise.all()`, which takes an array of promises and returns a new promise that resolves only when *all* of the input promises have resolved. This is perfect for when you need to run multiple asynchronous operations concurrently and wait for all of them to finish before proceeding. Conversely, `Promise.race()` resolves as soon as the *first* promise in the array resolves or rejects. Mastering these patterns is essential for writing modern, robust asynchronous code.