Developer implements Strategy and Adapter design patterns in JavaScript with tests

A developer completed a JavaScript design patterns exercise implementing the Strategy Pattern and the Adapter Pattern as part of a structured weekly learning task. The Strategy Pattern was applied to an e-commerce discount system, allowing different discount algorithms — flat, percentage, or none — to be swapped at runtime without modifying the core checkout logic. The Adapter Pattern was used to bridge an incompatible legacy payment gateway, which accepted amounts in cents via a different method name, with a modern application interface expecting a standard pay() call. Both implementations were verified using Node.js's built-in assert module to confirm correctness. The exercise highlighted how design patterns improve code flexibility, reduce complex conditional logic, and make systems easier to extend and maintain.