checkout Koa to see a great use case of generators. By yielding to asychronous code (instead of callbacks) you can write JS that looks like it's synchronous.
What is the advantage of using generators versus promises?
In this case, Koa uses generators and promises together to emulate the behavior of async/await style concurrency. You can see how Babel 5.x transforms ES7 async/await into generators and promises at https://github.com/babel/babel/blob/v5.8.34/packages/babel/s...