The factory pattern creates objects without exposing instantiation logic, providing flexibility to choose which class to instantiate at runtime. As the creator of CoreUI with 26 years of JavaScript development experience, I’ve implemented factory patterns in large-scale applications to manage component creation, handle multiple database adapters, and provide plugin architectures for millions of users.

The most maintainable approach uses factory functions or classes that encapsulate object creation logic.

The singleton pattern ensures a class has only one instance and provides a global access point to it, useful for managing shared resources like database connections, caches, or configuration. As the creator of CoreUI with 26 years of JavaScript development experience, I’ve implemented singletons in large-scale applications to manage global state, coordinate logging systems, and ensure single database connection pools across millions of requests.

The most maintainable approach uses ES6 modules for natural singleton behavior or static properties for class-based singletons.