Mastering Modular JavaScript

Chapter 2. Modularity Principles

Modularity can be the answer to complexity, but what exactly do we mean when we’re talking about complexity?

Complexity is a loaded term for a nuanced topic. What does complex mean? A dictionary defines complex as something that’s “composed of many interconnected parts” but that’s not the problem we generally refer to when we speak of complexity in the context of programming. A program may have hundreds or thousands of files and still be considered relatively simple.¹

The next two definitions, offered by that same dictionary, might be more revealing in the context of program design.

• “Characterized by a very complicated or involved arrangement of parts, units, etc.”

• “So complicated or intricate as to be hard to understand or deal with”

The first definition indicates that a program can become complex when its parts are arranged in a complicated manner; the interconnections among parts become a pain point. This could stem from convoluted interfaces or a lack of documentation, and it’s one of the aspects of complexity that we’ll tackle in this book.

We can interpret the second definition as the other side of the complexity coin. Components can be so complicated that their implementation is hard to understand, debug, or extend. Most of the book is devoted to counterbalancing and avoiding this aspect of complexity.

In broad terms, something is complex when it becomes hard to grasp or fully understand. By that definition, anything in a typical ...