Frontend Development Guidelines

Purpose

Comprehensive guide for modern React development, emphasizing Suspense-based data fetching, lazy loading, proper file organization, and performance optimization.

When to Use This Skill

• Creating new components or pages
• Building new features
• Fetching data with TanStack Query
• Setting up routing with TanStack Router
• Styling components with MUI v7
• Performance optimization
• Organizing frontend code
• TypeScript best practices

Quick Start

New Component Checklist

Creating a component? Follow this checklist:

• Use React.FC<Props> pattern with TypeScript
• Lazy load if heavy component: React.lazy(() => import())
• Wrap in <SuspenseLoader> for loading states
• Use useSuspenseQuery for data fetching
• Import aliases: @/, ~types, ~components, ~features
• Styles: Inline if <100 lines, separate file if >100 lines
• Use useCallback for event handlers passed to children
• Default export at bottom
• No early returns with loading spinners
• Use useMuiSnackbar for user notifications

New Feature Checklist

Creating a feature? Set up this structure:

• Create features/{feature-name}/ directory
• Create subdirectories: api/, components/, hooks/, helpers/, types/
• Create API service file: api/{feature}Api.ts
• Set up TypeScript types in types/
• Create route in routes/{feature-name}/index.tsx
• Lazy load feature components
• Use Suspense boundaries
• Export public API from feature index.ts

Import Aliases Quick Reference

Defined in: vite.config.ts lines 180-185

Common Imports Cheatsheet

typescript
1// React & Lazy Loading
2import React, { useState, useCallback, useMemo } from 'react';
3const Heavy = React.lazy(() => import('./Heavy'));
4
5// MUI Components
6import { Box, Paper, Typography, Button, Grid } from '@mui/material';
7import type { SxProps, Theme } from '@mui/material';
8
9// TanStack Query (Suspense)
10import { useSuspenseQuery, useQueryClient } from '@tanstack/react-query';
11
12// TanStack Router
13import { createFileRoute } from '@tanstack/react-router';
14
15// Project Components
16import { SuspenseLoader } from '~components/SuspenseLoader';
17
18// Hooks
19import { useAuth } from '@/hooks/useAuth';
20import { useMuiSnackbar } from '@/hooks/useMuiSnackbar';
21
22// Types
23import type { Post } from '~types/post';

Topic Guides

🎨 Component Patterns

Modern React components use:

• React.FC<Props> for type safety
• React.lazy() for code splitting
• SuspenseLoader for loading states
• Named const + default export pattern

Key Concepts:

• Lazy load heavy components (DataGrid, charts, editors)
• Always wrap lazy components in Suspense
• Use SuspenseLoader component (with fade animation)
• Component structure: Props → Hooks → Handlers → Render → Export

📖 Complete Guide: resources/component-patterns.md

📊 Data Fetching

PRIMARY PATTERN: useSuspenseQuery

• Use with Suspense boundaries
• Cache-first strategy (check grid cache before API)
• Replaces isLoading checks
• Type-safe with generics

API Service Layer:

• Create features/{feature}/api/{feature}Api.ts
• Use apiClient axios instance
• Centralized methods per feature
• Route format: /form/route (NOT /api/form/route)

📖 Complete Guide: resources/data-fetching.md

📁 File Organization

features/ vs components/:

• features/: Domain-specific (posts, comments, auth)
• components/: Truly reusable (SuspenseLoader, CustomAppBar)

Feature Subdirectories:

features/
  my-feature/
    api/          # API service layer
    components/   # Feature components
    hooks/        # Custom hooks
    helpers/      # Utility functions
    types/        # TypeScript types

📖 Complete Guide: resources/file-organization.md

🎨 Styling

Inline vs Separate:

• <100 lines: Inline const styles: Record<string, SxProps<Theme>>

• 100 lines: Separate .styles.ts file

Primary Method:

• Use sx prop for MUI components
• Type-safe with SxProps<Theme>
• Theme access: (theme) => theme.palette.primary.main

MUI v7 Grid:

typescript
1<Grid size={{ xs: 12, md: 6 }}>  // ✅ v7 syntax
2<Grid xs={12} md={6}>             // ❌ Old syntax

📖 Complete Guide: resources/styling-guide.md

🛣️ Routing

TanStack Router - Folder-Based:

• Directory: routes/my-route/index.tsx
• Lazy load components
• Use createFileRoute
• Breadcrumb data in loader

Example:

typescript
1import { createFileRoute } from '@tanstack/react-router';
2import { lazy } from 'react';
3
4const MyPage = lazy(() => import('@/features/my-feature/components/MyPage'));
5
6export const Route = createFileRoute('/my-route/')({
7    component: MyPage,
8    loader: () => ({ crumb: 'My Route' }),
9});

📖 Complete Guide: resources/routing-guide.md

⏳ Loading & Error States

CRITICAL RULE: No Early Returns

typescript
1// ❌ NEVER - Causes layout shift
2if (isLoading) {
3    return <LoadingSpinner />;
4}
5
6// ✅ ALWAYS - Consistent layout
7<SuspenseLoader>
8    <Content />
9</SuspenseLoader>

Why: Prevents Cumulative Layout Shift (CLS), better UX

Error Handling:

• Use useMuiSnackbar for user feedback
• NEVER react-toastify
• TanStack Query onError callbacks

📖 Complete Guide: resources/loading-and-error-states.md

⚡ Performance

Optimization Patterns:

• useMemo: Expensive computations (filter, sort, map)
• useCallback: Event handlers passed to children
• React.memo: Expensive components
• Debounced search (300-500ms)
• Memory leak prevention (cleanup in useEffect)

📖 Complete Guide: resources/performance.md

📘 TypeScript

Standards:

• Strict mode, no any type
• Explicit return types on functions
• Type imports: import type { User } from '~types/user'
• Component prop interfaces with JSDoc

📖 Complete Guide: resources/typescript-standards.md

🔧 Common Patterns

Covered Topics:

• React Hook Form with Zod validation
• DataGrid wrapper contracts
• Dialog component standards
• useAuth hook for current user
• Mutation patterns with cache invalidation

📖 Complete Guide: resources/common-patterns.md

👤 User Avatars

ALWAYS use AvatarUrl helper for user avatars - handles empty strings, Discord IDs, and fallback generation.

typescript
1import { AvatarUrl } from "~/components/user/avatar";
2<img src={AvatarUrl(user)} />

📖 Complete Guide: resources/user-avatar.md

📚 Complete Examples

Full working examples:

• Modern component with all patterns
• Complete feature structure
• API service layer
• Route with lazy loading
• Suspense + useSuspenseQuery
• Form with validation

📖 Complete Guide: resources/complete-examples.md

Navigation Guide

Core Principles

1. Lazy Load Everything Heavy: Routes, DataGrid, charts, editors
2. Suspense for Loading: Use SuspenseLoader, not early returns
3. useSuspenseQuery: Primary data fetching pattern for new code
4. Features are Organized: api/, components/, hooks/, helpers/ subdirs
5. Styles Based on Size: <100 inline, >100 separate
6. Import Aliases: Use @/, ~types, ~components, ~features
7. No Early Returns: Prevents layout shift
8. useMuiSnackbar: For all user notifications

Quick Reference: File Structure

src/
  features/
    my-feature/
      api/
        myFeatureApi.ts       # API service
      components/
        MyFeature.tsx         # Main component
        SubComponent.tsx      # Related components
      hooks/
        useMyFeature.ts       # Custom hooks
        useSuspenseMyFeature.ts  # Suspense hooks
      helpers/
        myFeatureHelpers.ts   # Utilities
      types/
        index.ts              # TypeScript types
      index.ts                # Public exports

  components/
    SuspenseLoader/
      SuspenseLoader.tsx      # Reusable loader
    CustomAppBar/
      CustomAppBar.tsx        # Reusable app bar

  routes/
    my-route/
      index.tsx               # Route component
      create/
        index.tsx             # Nested route

Modern Component Template (Quick Copy)

typescript
1import React, { useState, useCallback } from 'react';
2import { Box, Paper } from '@mui/material';
3import { useSuspenseQuery } from '@tanstack/react-query';
4import { featureApi } from '../api/featureApi';
5import type { FeatureData } from '~types/feature';
6
7interface MyComponentProps {
8    id: number;
9    onAction?: () => void;
10}
11
12export const MyComponent: React.FC<MyComponentProps> = ({ id, onAction }) => {
13    const [state, setState] = useState<string>('');
14
15    const { data } = useSuspenseQuery({
16        queryKey: ['feature', id],
17        queryFn: () => featureApi.getFeature(id),
18    });
19
20    const handleAction = useCallback(() => {
21        setState('updated');
22        onAction?.();
23    }, [onAction]);
24
25    return (
26        <Box sx={{ p: 2 }}>
27            <Paper sx={{ p: 3 }}>
28                {/* Content */}
29            </Paper>
30        </Box>
31    );
32};
33
34export default MyComponent;

For complete examples, see resources/complete-examples.md

Related Skills

• error-tracking: Error tracking with Sentry (applies to frontend too)
• backend-dev-guidelines: Backend API patterns that frontend consumes

Skill Status: Modular structure with progressive loading for optimal context management