Hands-On Functional Programming with TypeScript

Asynchronous generators

We have already learned about the interface implemented by all iterators:

interface Iterator<T> {  next(value?: any): IteratorResult<T>;  return?(value?: any): IteratorResult<T>;  throw?(e?: any): IteratorResult<T>;}

However, we haven't learned yet about the interface implemented by all asynchronous iterators:

interface AsyncIterator<T> {  next(value?: any): Promise<IteratorResult<T>>;  return?(value?: any): Promise<IteratorResult<T>>;  throw?(e?: any): Promise<IteratorResult<T>>;}

An asynchronous iterator returns a promise every time we invoke the next method. The following code snippet demonstrates how asynchronous iterators can be very useful when used in conjunction with asynchronous functions:

let counter = 0;function ...