CommonJS vs ESM, Design Patterns, and Memory Management in JavaScript

A developer documented key JavaScript concepts including the differences between CommonJS and ES Modules, two systems used to split code across files and manage dependencies. CommonJS, widely used in Node.js, relies on require() and module.exports with synchronous loading, while ESM uses static import/export syntax supported by both browsers and modern Node.js. The article also covered JavaScript's garbage collection mechanism, specifically the Mark-and-Sweep model, which removes objects that are no longer reachable in memory. Closures were explained as functions that retain access to their outer scope even after execution, and the piece clarified that closures only cause memory leaks when they unintentionally keep references alive longer than needed. Finally, the writeup introduced design patterns as reusable solutions to common software architecture problems.