Data mutation and state management are major sources of incidental complexity, which can make developing and debugging applications much more difficult. Browser­based applications,in particular, are inherently tied to mutability through the DOM. Embracing immutability allows us to write pure and declarative code that is modular, and can be understood without reasoning about other parts of the system.

ClojureScript is a functional language that compiles to JavaScript, and all data is immutable by default. Combined with Facebook’s React, a library that provides a functional interface to the DOM by managing mutability, we can build client­side applications with surprisingly lower complexity, new capabilities, and better performance than more common approaches.

In this talk, we will explore the design and implications of an architecture built around immutable data structures using ClojureScript and Om, a ClojureScript interface to React.