Recursion and iteration are two alternative paradigms for solving problems by breaking them down into smaller chunks; this talk is a deep dive into how these paradigms work, and how JS supports them both. There’s a fundamental tradeoff between the two: the stateful repetition of iteration is often more performant as it’s closer to the way our machines “think”, whereas many programmers find the self-referential abstraction of recursion easier to read & write. In JS prior to ES6, neither paradigm was especially easy to work with: iterative loops were laborious to read and write (not human-efficient), and recursion was limited by the fact that subsequent recursive calls to a function require additional frames added to the stack, potentially leading to stack overflow (not machine-efficient). Eventually, however, all three - recursion, iteration, and JS - were finally brought closer together. In this talk we’ll dive into the nature of the two paradigms, examine what an Iterable and a tail-recursive function are, and learn how Tail Call Optimization unites the two paradigms, allowing us to write code recursively and run it iteratively.