---
id: T01
parent: S06
milestone: M016
provides: []
requires: []
affects: []
key_files: ["frontend/src/hooks/useCountUp.ts", "frontend/src/pages/Home.tsx"]
key_decisions: ["Made useCountUp generic over element type for React 18 ref compatibility", "Each hook instance owns its own IntersectionObserver rather than sharing"]
patterns_established: []
drill_down_paths: []
observability_surfaces: []
duration: ""
verification_result: "TypeScript compilation passes with zero errors. Vite production build succeeds (59 modules). useCountUp.ts exists. Home.tsx imports and uses useCountUp."
completed_at: 2026-04-03T06:18:57.030Z
blocker_discovered: false
---

# T01: Created generic useCountUp hook with IntersectionObserver-triggered rAF animation and wired it into Home.tsx stats section

> Created generic useCountUp hook with IntersectionObserver-triggered rAF animation and wired it into Home.tsx stats section

## What Happened
---
id: T01
parent: S06
milestone: M016
key_files:
  - frontend/src/hooks/useCountUp.ts
  - frontend/src/pages/Home.tsx
key_decisions:
  - Made useCountUp generic over element type for React 18 ref compatibility
  - Each hook instance owns its own IntersectionObserver rather than sharing
duration: ""
verification_result: passed
completed_at: 2026-04-03T06:18:57.030Z
blocker_discovered: false
---

# T01: Created generic useCountUp hook with IntersectionObserver-triggered rAF animation and wired it into Home.tsx stats section

**Created generic useCountUp hook with IntersectionObserver-triggered rAF animation and wired it into Home.tsx stats section**

## What Happened

Created `frontend/src/hooks/useCountUp.ts` — a reusable hook that animates from 0 to a target number using requestAnimationFrame with cubic ease-out timing. Uses IntersectionObserver (threshold 0.3) to trigger animation when scrolled into view, fires once per mount. Handles async data loading by resetting when target changes from 0 to a positive value. Made the hook generic over element type to satisfy React 18's strict ref typing. Wired both technique_count and creator_count into Home.tsx as animated values.

## Verification

TypeScript compilation passes with zero errors. Vite production build succeeds (59 modules). useCountUp.ts exists. Home.tsx imports and uses useCountUp.

## Verification Evidence

| # | Command | Exit Code | Verdict | Duration |
|---|---------|-----------|---------|----------|
| 1 | `cd frontend && npx tsc --noEmit` | 0 | ✅ pass | 8000ms |
| 2 | `cd frontend && npm run build` | 0 | ✅ pass | 2000ms |
| 3 | `test -f src/hooks/useCountUp.ts` | 0 | ✅ pass | 100ms |
| 4 | `grep -q 'useCountUp' src/pages/Home.tsx` | 0 | ✅ pass | 100ms |


## Deviations

Made hook generic (useCountUp<T extends HTMLElement>) to satisfy React 18 strict ref typing — not in original plan but required. Used separate ref per hook instance instead of shared ref.

## Known Issues

None.

## Files Created/Modified

- `frontend/src/hooks/useCountUp.ts`
- `frontend/src/pages/Home.tsx`


## Deviations
Made hook generic (useCountUp<T extends HTMLElement>) to satisfy React 18 strict ref typing — not in original plan but required. Used separate ref per hook instance instead of shared ref.

## Known Issues
None.
