How do you wrap a callback-based API into a Promise?

This tests whether you understand the Promise constructor as a bridge between legacy callback APIs and modern async patterns. A complete answer returns a new Promise that wraps the legacy call, passes a callback that resolves with the value on success and rejects with the error on failure, and ensures the wrapper function returns that Promise. A red flag is forgetting to handle the error case, calling resolve with an error, or returning the legacy function's undefined return value instead of the Promise object.