...It focuses on three architectural “ilities”: readability, reusability, and refactorability, presenting them in a hierarchical framework so developers can evaluate and improve their code and system design. The project uses a simple shopping-cart application written in JavaScript and React/Redux to illustrate how code evolves from “bad” via “better” to “good” across those three dimensions. By examining common smells—poor naming, deep nesting, long functions, tight coupling—readers learn how to restructure code to improve maintainability. It is targeted at developers of any experience level, though beginners will find its concrete examples especially useful. ...