Context

In frontend and application programming, local collection state is updated frequently when users add items. Interviewers ask this to assess whether you understand safe state updates, data structure choices, and how changes propagate through the UI.

Core question

Explain how you would manage the local state for a garment list when a new item is added.

Address these points:

1. How you would store the garment list in local state and append a new garment.
2. Why immutable updates are preferred over mutating the existing list directly.
3. How you would handle practical concerns such as duplicate IDs, ordering, and rendering efficiency.

Scope guidance

The interviewer expects a clear explanation of the update pattern, the underlying data structure behavior, and common pitfalls. You should discuss both the straightforward array/list approach and when you might add supporting structures such as a hash map or set for validation or fast lookup.