A value that is either T directly or a Promise<T>.
T
Promise<T>
Used in callback signatures that support both synchronous and asynchronous returns (e.g. instructions), so adopters can return either a plain string or an async function without separate overloads.
instructions
async
A value that is either
Tdirectly or aPromise<T>.Used in callback signatures that support both synchronous and asynchronous returns (e.g.
instructions), so adopters can return either a plain string or anasyncfunction without separate overloads.