Lately I've been learning a lot about node.js and the surrounding library ecosystem. Some of the libraries I've come across have been what's been called "middleware" frameworks. These are libraries like Connect.js and Flatiron.
I'm wondering if middleware is a reasonable form of modularity, pros and cons, and comparison to built-in structures for modularity: functions and objects.
I came across this interesting question (and answer), which gives the opinion that one probably shouldn't use these kinds of middleware frameworks. Is it because they aren't robust forms of modularity?