Generators

The ES6 specification introduces another mechanism that, besides other things, can be used to simplify the asynchronous control flow of our Node.js applications. We are talking about generators, also known as semi-coroutines. They are a generalization of subroutines, where there can be different entry points. In a normal function, in fact, we can have only one entry point, which corresponds to the invocation of the function itself. A generator is similar to a function, but in addition, it can be suspended (using the yield statement) and then resumed at a later time. Generators are particularly useful when implementing iterators, and this should ring a bell, as we have already seen how iterators can be used to implement important asynchronous control flow patterns such as sequential and limited parallel execution.

Note

In Node.js, generators are available starting from Version 0.11, but at the moment of writing, this feature is still not enabled by default and it's necessary to...