Design a client-side comment system

## Scenario You are asked to build a **client-side comment system** (no backend required). The focus is on data modeling, UI behavior, and persistence. ## Requirements 1. **Create and display comments** - A user can add a new top-level comment with: `id`, `author` (optional), `text`, `createdAt`. - Render a list of comments. 2. **Filter and sort comments** - Provide a way to **sort** comments (e.g., `Newest first` / `Oldest first`). - Provide a way to **filter** comments (e.g., by keyword in `text`, or show only comments from a given author). - Sorting/filtering should apply to the rendered list. 3. **Nested comments (replies)** - Each comment can have replies (nested comments), forming a tree. - Users can reply to any comment. - Nested comments should also respect the current sort/filter behavior (define your rules). 4. **Persistence with `localStorage`** - Persist the comment data so a page refresh restores the comments. - Also persist the user’s **current sort choice** (and filter choice if applicable). ## Constraints / clarifications - Assume a single browser tab (no multi-user concurrency). - You may choose any UI approach (vanilla JS, React, etc.), but your design should be framework-agnostic. - Explain how you would structure the state, how you would store it in `localStorage`, and how you would handle updates efficiently. ## Deliverables (in interview) - Data model (types / JSON structure) - Key functions/APIs (add comment, reply, set sort/filter, load/save) - Explanation of rendering strategy for nested comments - Edge cases and tradeoffs