Javascript Fundamentals

This covers the core JavaScript concepts you'd actually use daily: closures, prototypes, async patterns, and ES6+ features like arrow functions and classes. The examples are solid and practical, showing both the old constructor function approach and modern class syntax, plus real use cases for closures beyond the typical counter example. It's comprehensive enough for code reviews or explaining tricky concepts to teammates, but doesn't waste time on trivial stuff. The variable scoping comparison between var, let, and const is especially useful since that trips people up constantly. Good for both writing new code and modernizing legacy codebases that still use outdated patterns.