Since we are using Flow, and Node doesn't actually know about the data types, there will obviously be problems if we just try to execute our data-typed code. There are two solutions for this: one not so elegant, but that speeds up development, and another more powerful one, but that will require extra work. Let's here consider the first, simpler solution, and leave the second one for the next section.
Using Flow with Node, directly
How to do it...
It so happens that Flow provides two ways of specifying types: the way that we have been using so far, with extra type notations, and another more verbose one, through the comments. Of course, JS doesn't know about type definitions, so the first style won't work...
