When OOP fits JS and TS

OOP fits when identity, lifecycle, invariants, and polymorphic behavior dominate—domain entities, state machines, plugin registries, UI controllers with long-lived state. Functional pipelines excel at data transformation, parsing, and parallel maps over collections.

JS is multi-paradigm: prototypes under classes, first-class functions everywhere. TS adds types to either style without forcing inheritance.

On interviews: pick OOP vs functions for a shopping cart versus CSV import pipeline and justify.

Common pitfalls: Java-style hierarchies in a language favoring composition, classes as namespace holders, and OOP where plain functions plus types suffice.

The trade-off is familiar entity modeling versus idiomatic JS simplicity—match paradigm to change patterns.

Checklist:

• OOP for entities with identity and rules.
• Functions for stateless transforms.
• Avoid inheritance depth in JS codebases.