createReducer on() vs Switch-Case Reducers for State Immutability

State Management Strategy for Small-Scale Applications

When migrating a small Angular application to NgRx, the choice of reducer implementation affects both long-term maintainability and the risk of accidental state mutation. The goal is to ensure strict immutability while keeping the codebase accessible for a small team.

The createReducer utility with on() provides a declarative API designed to enforce immutable updates. Conversely, the classic switch-case reducer pattern relies on manual state copying via the spread operator, which is often more familiar to developers but increases the risk of mutating nested references.

For an application with frequent, large state updates, there is a trade-off between the safety of the createReducer API and the debugging simplicity of a standard function block.

• Does createReducer provide significant protection against nested mutation compared to a disciplined switch-case implementation?
• Which approach minimizes boilerplate and improves readability when managing deeply nested state objects in NgRx v15+?