What is the main difference between factory functions and constructor functions?
Key differences between factory and constructor functions: 1) Constructor functions require 'new' keyword, factory functions don't, 2) Constructor functions automatically set up prototype chain, factory functions need explicit prototype setup, 3) Factory functions can easily implement privacy through closures, 4) Constructor functions use 'this' binding, factory functions use regular object creation, 5) Factory functions provide more flexibility in object creation, 6) Constructor functions are more memory efficient for methods through shared prototype.