A complete tour of JavaScript modules — the historical landscape (IIFE, AMD UMD, CommonJS), modern ES modules (export/import, default vs named re-exports dynamic import), interop between ESM and CJS in Node, package.json exports and how TypeScript and bundlers fit in.

A practical introduction to functional programming in JavaScript — pure functions, immutability, first-class and higher-order functions, composition currying, the standard-library toolkit, and where the discipline ends and pragmatism begins.