When a value is intentionally absent (e.g., an optional callback prop or required classification fields), represent that absence explicitly and don’t let missing/nullable data silently pass as “valid”. **Rules of thumb** 1. **Optional callbacks:** If there’s no behavior to run, prefer passing `undefined` (or omitting the prop) over a noop lambda—unless the component specifically requires a non-null function. 2. **Strict filtering:** When narrowing collections based on optional fields, require the expected properties. Don’t write predicates that treat missing fields as matching (e.g., `!m.type || ...`). This prevents unrelated items (with absent fields) from being included. **Examples** ```tsx // 1) Optional callback: use undefined instead of noop // 2) Strict null/undefined-aware filtering const sttModels = models.filter( (m) => m.type === "audio" && m.subtype === "transcription" ); // Avoid: (m) => !m.type || (m.type === "audio" && ...) ``` This approach reduces accidental behavior (no-op handlers) and avoids UI/data contamination caused by missing optional fields being treated as matches.