Frontend Dev Guidelines

Frontend Development Guidelines

(React · TypeScript · Suspense-First · Production-Grade)

You are a senior frontend engineer operating under strict architectural and performance standards.

Your goal is to build scalable, predictable, and maintainable React applications using:

• Suspense-first data fetching
• Feature-based code organization
• Strict TypeScript discipline
• Performance-safe defaults

This skill defines how frontend code must be written, not merely how it can be written.

---

1. Frontend Feasibility & Complexity Index (FFCI)

Before implementing a component, page, or feature, assess feasibility.

FFCI Dimensions (1–5)

| Dimension | Question | | --------------------- | ---------------------------------------------------------------- | | Architectural Fit | Does this align with feature-based structure and Suspense model? | | Complexity Load | How complex is state, data, and interaction logic? | | Performance Risk | Does it introduce rendering, bundle, or CLS risk? | | Reusability | Can this be reused without modification? | | Maintenance Cost | How hard will this be to reason about in 6 months? |

Score Formula

FFCI = (Architectural Fit + Reusability + Performance) − (Complexity + Maintenance Cost)

Range: -5 → +15

Interpretation

| FFCI | Meaning | Action | | --------- | ---------- | ----------------- | | 10–15 | Excellent | Proceed | | 6–9 | Acceptable | Proceed with care | | 3–5 | Risky | Simplify or split | | ≤ 2 | Poor | Redesign |

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2. Core Architectural Doctrine (Non-Negotiable)

1. Suspense Is the Default

• useSuspenseQuery is the primary data-fetching hook
• No isLoading conditionals
• No early-return spinners

2. Lazy Load Anything Heavy

• Routes
• Feature entry components
• Data grids, charts, editors
• Large dialogs or modals

3. Feature-Based Organization

• Domain logic lives in features/
• Reusable primitives live in components/
• Cross-feature coupling is forbidden

4. TypeScript Is Strict

• No any
• Explicit return types
• import type always
• Types are first-class design artifacts

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When to Use

Use frontend-dev-guidelines when:

• Creating components or pages
• Adding new features
• Fetching or mutating data
• Setting up routing
• Styling with MUI
• Addressing performance issues
• Reviewing or refactoring frontend code

---

3. Quick Start Checklists

New Component Checklist

• [ ] React.FC with explicit props interface
• [ ] Lazy loaded if non-trivial
• [ ] Wrapped in ``
• [ ] Uses useSuspenseQuery for data
• [ ] No early returns
• [ ] Handlers wrapped in useCallback
• [ ] Styles inline if import('./HeavyComponent'));

Always wrapped in ``.

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## 6. Data Fetching Doctrine

### Primary Pattern

* `useSuspenseQuery`
* Cache-first
* Typed responses

### Forbidden Patterns

❌ `isLoading`
❌ manual spinners
❌ fetch logic inside components
❌ API calls without feature API layer

### API Layer Rules

* One API file per feature
* No inline axios calls
* No `/api/` prefix in routes

---

## 7. Routing Standards (TanStack Router)

* Folder-based routing only
* Lazy load route components
* Breadcrumb metadata via loaders

```ts
export const Route = createFileRoute('/my-route/')({
  component: MyPage,
  loader: () => ({ crumb: 'My Route' }),
});

---

8. Styling Standards (MUI v7)

Inline vs Separate

• 100 lines: {Component}.styles.ts

Grid Syntax (v7 Only)

 // ✅
          // ❌

Theme access must always be type-safe.

---

9. Loading & Error Handling

Absolute Rule

❌ Never return early loaders ✅ Always rely on Suspense boundaries

User Feedback

• useMuiSnackbar only
• No third-party toast libraries

---

10. Performance Defaults

• useMemo for expensive derivations
• useCallback for passed handlers
• React.memo for heavy pure components
• Debounce search (300–500ms)
• Cleanup effects to avoid leaks

Performance regressions are bugs.

---

11. TypeScript Standards

• Strict mode enabled
• No implicit any
• Explicit return types
• JSDoc on public interfaces
• Types colocated with feature

---

12. Canonical File Structure

src/
  features/
    my-feature/
      api/
      components/
      hooks/
      helpers/
      types/
      index.ts

  components/
    SuspenseLoader/
    CustomAppBar/

  routes/
    my-route/
      index.tsx

---

13. Canonical Component Template

import React, { useState, useCallback } from 'react';
import { Box, Paper } from '@mui/material';
import { useSuspenseQuery } from '@tanstack/react-query';
import { featureApi } from '../api/featureApi';
import type { FeatureData } from '~types/feature';

interface MyComponentProps {
  id: number;
  onAction?: () => void;
}

export const MyComponent: React.FC = ({ id, onAction }) => {
  const [state, setState] = useState('');

  const { data } = useSuspenseQuery({
    queryKey: ['feature', id],
    queryFn: () => featureApi.getFeature(id),
  });

  const handleAction = useCallback(() => {
    setState('updated');
    onAction?.();
  }, [onAction]);

  return (
    
      
        {/* Content */}
      
    
  );
};

export default MyComponent;

---

14. Anti-Patterns (Immediate Rejection)

❌ Early loading returns ❌ Feature logic in components/ ❌ Shared state via prop drilling instead of hooks ❌ Inline API calls ❌ Untyped responses ❌ Multiple responsibilities in one component

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15. Integration With Other Skills

• frontend-design → Visual systems & aesthetics
• page-cro → Layout hierarchy & conversion logic
• analytics-tracking → Event instrumentation
• backend-dev-guidelines → API contract alignment
• error-tracking → Runtime observability

---

16. Operator Validation Checklist

Before finalizing code:

• [ ] FFCI ≥ 6
• [ ] Suspense used correctly
• [ ] Feature boundaries respected
• [ ] No early returns
• [ ] Types explicit and correct
• [ ] Lazy loading applied
• [ ] Performance safe

---

17. Skill Status

Status: Stable, opinionated, and enforceable Intended Use: Production React codebases with long-term maintenance horizons

When to Use

This skill is applicable to execute the workflow or actions described in the overview.

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: KunanonJ
• Source: KunanonJ/ai-skills-hub
• License: MIT

Install and usage instructions live in the source repository linked above.