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:

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

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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

2. Lazy Load Anything Heavy

3. Feature-Based Organization

4. TypeScript Is Strict

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3. When to Use This Skill

Use frontend-dev-guidelines when:

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4. Quick Start Checklists

New Component Checklist

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New Feature Checklist

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5. Import Aliases (Required)

| Alias | Path |

| ------------- | ---------------- |

| @/ | src/ |

| ~types | src/types |

| ~components | src/components |

| ~features | src/features |

Aliases must be used consistently. Relative imports beyond one level are discouraged.

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6. Component Standards

Required Structure Order

Lazy Loading Pattern

const HeavyComponent = React.lazy(() => import('./HeavyComponent'));

Always wrapped in .

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7. Data Fetching Doctrine

Primary Pattern

Forbidden Patterns

❌ isLoading

❌ manual spinners

❌ fetch logic inside components

❌ API calls without feature API layer

API Layer Rules

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8. Routing Standards (TanStack Router)

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

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9. Styling Standards (MUI v7)

Inline vs Separate

Grid Syntax (v7 Only)

<Grid size={{ xs: 12, md: 6 }} /> // ✅
<Grid xs={12} md={6} />          // ❌

Theme access must always be type-safe.

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10. Loading & Error Handling

Absolute Rule

❌ Never return early loaders

✅ Always rely on Suspense boundaries

User Feedback

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11. Performance Defaults

Performance regressions are bugs.

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12. TypeScript Standards

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13. Canonical File Structure

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

  components/
    SuspenseLoader/
    CustomAppBar/

  routes/
    my-route/
      index.tsx

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14. 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<MyComponentProps> = ({ id, onAction }) => {
  const [state, setState] = useState('');

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

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

  return (
    <Box sx={{ p: 2 }}>
      <Paper sx={{ p: 3 }}>
        {/* Content */}
      </Paper>
    </Box>
  );
};

export default MyComponent;

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15. 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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16. Integration With Other Skills

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17. Operator Validation Checklist

Before finalizing code:

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18. Skill Status

Status: Stable, opinionated, and enforceable

Intended Use: Production React codebases with long-term maintenance horizons