How can JavaScript be used responsibly in model-driven apps, and when should developers avoid client-side customization?

JavaScript can extend model-driven apps when client-side behavior cannot be achieved through standard Dataverse capabilities or configuration. Developers should understand appropriate use cases such as form events, field interactions, validation, and UI behavior while avoiding unnecessary customization that increases technical debt. Business Rules, business process capabilities, Power Automate, and server-side logic should be considered before introducing JavaScript. Learning when not to write JavaScript is just as important as knowing how to write it in a maintainable Dynamics 365 CE solution.