The difficulties of asynchronous programming

Losing control of asynchronous code in JavaScript is undoubtedly easy. Closures and in-place definition of anonymous functions allow a smooth programming experience that doesn't require the developer to jump to other points in the code base. This is perfectly in line with the KISS principle; it's simple, it keeps the code flowing, and we get it working in less time. Unfortunately, sacrificing qualities such as modularity, reusability, and maintainability will sooner or later lead to the uncontrolled proliferation of callback nesting, the growth in the size of functions, and will lead to poor code organization. Most of the time, creating closures is not functionally needed, so it's more a matter of discipline than a problem related to asynchronous programming. Recognizing that our code is becoming unwieldy—or even better, knowing in advance that it might become unwieldy—and then acting accordingly with the most adequate solution is what differentiates...