Frontend Development Guidelines

Purpose

Comprehensive guide for modern frontend development across React, Vue 3, Svelte 5, and Angular. Covers framework-specific patterns, common architectural principles, and cross-framework best practices.

When to Use This Skill

• Creating components or pages in React, Vue, Svelte, or Angular
• Building new features with framework-specific patterns
• Implementing state management (Pinia, Zustand, stores, signals)
• Setting up routing (TanStack Router, Vue Router, SvelteKit, Angular Router)
• Data fetching patterns (TanStack Query, composables, SvelteKit load functions)
• Performance optimization across frameworks
• Component composition and reusability
• TypeScript integration and best practices
• Choosing the right framework for a project
• Migrating between frameworks

Framework Selection Guide

Choose your framework based on project requirements:

Quick Decision:

• Existing codebase? Use what's there or plan migration
• Team experience? Leverage existing knowledge
• Project size? Large → React/Angular, Medium → Vue/React, Small → Svelte/Vue
• Performance critical? Svelte > Vue > React ≈ Angular
• TypeScript required? All support it well (Angular best integrated)
• Ecosystem needs? React > Vue > Angular > Svelte

See framework-specific sections below for detailed patterns.

Quick Framework Comparison

Jump to:

• React Development - Hooks, Suspense, TanStack ecosystem
• Vue 3 Development - Composition API, Pinia, Nuxt
• Svelte 5 Development - Runes, SvelteKit, minimal runtime
• Angular Development - Signals, standalone components, RxJS
• Framework-Agnostic Patterns - Universal concepts

React Development

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

// React & Lazy Loading
import React, { useState, useCallback, useMemo } from 'react';
const Heavy = React.lazy(() => import('./Heavy'));

// MUI Components
import { Box, Paper, Typography, Button, Grid } from '@mui/material';
import type { SxProps, Theme } from '@mui/material';

// TanStack Query (Suspense)
import { useSuspenseQuery, useQueryClient } from '@tanstack/react-query';

// TanStack Router
import { createFileRoute } from '@tanstack/react-router';

// Project Components
import { SuspenseLoader } from '~components/SuspenseLoader';

// Hooks
import { useAuth } from '@/hooks/useAuth';
import { useMuiSnackbar } from '@/hooks/useMuiSnackbar';

// Types
import 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:

<Grid size={{ xs: 12, md: 6 }}>  // ✅ v7 syntax
<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:

import { createFileRoute } from '@tanstack/react-router';
import { lazy } from 'react';

const MyPage = lazy(() => import('@/features/my-feature/components/MyPage'));

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

📖 Complete Guide: resources/routing-guide.md

⏳ Loading & Error States

CRITICAL RULE: No Early Returns

// ❌ NEVER - Causes layout shift
if (isLoading) {
    return <LoadingSpinner />;
}

// ✅ ALWAYS - Consistent layout
<SuspenseLoader>
    <Content />
</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

📚 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

React-Specific Navigation Guide

Note: Resources above are React-specific. For Vue/Svelte/Angular, see framework sections in this document.

Core Principles (All Frameworks)

1. Lazy Load Heavy Components: Routes, data grids, charts, editors, modals
2. Consistent Loading States: Avoid layout shift with proper loading UI
3. Type Safety: Use TypeScript for all components and APIs
4. Component Composition: Small, focused components with clear responsibilities
5. Unidirectional Data Flow: Props down, events up
6. Performance First: Memoize expensive computations, virtual scrolling for lists
7. Organized Features: Group related code (components, state, types, utilities)
8. Framework Idioms: Use framework-specific patterns (hooks, composables, runes, services)

React-Specific Principles

1. useSuspenseQuery: Primary data fetching pattern for new code
2. No Early Returns: Prevents layout shift (use Suspense boundaries)
3. Import Aliases: Use @/, ~types, ~components, ~features
4. Styles Based on Size: <100 inline, >100 separate file

Vue-Specific Principles

1. Composition API: Prefer over Options API for reusability
2. Script Setup: Use for cleaner syntax and better performance
3. Composables: Extract reusable logic like React hooks
4. Pinia for State: Modern Vuex alternative with TypeScript support

Svelte-Specific Principles

1. Runes for Reactivity: Use $state, $derived, $effect (Svelte 5+)
2. SvelteKit for Apps: Leverage file-based routing and server functions
3. Minimal Stores: Runes reduce need for stores in components
4. Progressive Enhancement: Build for no-JS, enhance with JS

Angular-Specific Principles

1. Standalone Components: Default since v17 (avoid NgModules)
2. Signals for State: Prefer over RxJS for simple reactivity
3. OnPush Detection: Optimize change detection
4. Dependency Injection: Use inject() for modern DI

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)

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<string>('');

    const { data } = useSuspenseQuery({
        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;

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

Vue 3 Development

Component Patterns

Composition API - Modern Vue 3 approach with <script setup>:

<script setup lang="ts">
import { ref, computed, onMounted } from 'vue'
import type { User } from '@/types/user'

interface Props {
  userId: number
}

const props = defineProps<Props>()
const emit = defineEmits<{
  update: [user: User]
}>()

const user = ref<User | null>(null)
const isLoading = ref(true)
const displayName = computed(() => user.value?.name ?? 'Unknown')

onMounted(async () => {
  user.value = await fetchUser(props.userId)
  isLoading.value = false
})

function handleUpdate() {
  if (user.value) emit('update', user.value)
}
</script>

<template>
  <div class="user-profile">
    <div v-if="isLoading">Loading...</div>
    <div v-else>
      <h2>{{ displayName }}</h2>
      <button @click="handleUpdate">Update</button>
    </div>
  </div>
</template>

<style scoped>
.user-profile {
  padding: 1rem;
}
</style>

Key Patterns:

• <script setup> - Concise composition API syntax
• defineProps<T>() - Type-safe props with generics
• defineEmits<T>() - Type-safe events
• ref(), reactive() - Reactivity primitives
• computed() - Derived state
• watch(), watchEffect() - Side effects
• onMounted, onUnmounted - Lifecycle hooks

State Management (Pinia)

// stores/userStore.ts
import { defineStore } from 'pinia'
import { ref, computed } from 'vue'

export const useUserStore = defineStore('user', () => {
  // State
  const users = ref<User[]>([])
  const currentUser = ref<User | null>(null)

  // Getters
  const userCount = computed(() => users.value.length)
  const isAuthenticated = computed(() => currentUser.value !== null)

  // Actions
  async function fetchUsers() {
    users.value = await api.getUsers()
  }

  function setCurrentUser(user: User) {
    currentUser.value = user
  }

  return { users, currentUser, userCount, isAuthenticated, fetchUsers, setCurrentUser }
})

// Component usage
<script setup lang="ts">
import { useUserStore } from '@/stores/userStore'
const userStore = useUserStore()
</script>

Routing (Vue Router)

// router/index.ts
import { createRouter, createWebHistory } from 'vue-router'

const router = createRouter({
  history: createWebHistory(),
  routes: [
    {
      path: '/',
      component: () => import('@/views/HomeView.vue')
    },
    {
      path: '/users/:id',
      component: () => import('@/views/UserView.vue'),
      props: true
    }
  ]
})

// Component with route params
<script setup lang="ts">
import { useRoute, useRouter } from 'vue-router'

const route = useRoute()
const router = useRouter()
const userId = route.params.id

function goBack() {
  router.push('/')
}
</script>

Data Fetching Patterns

Composables - Reusable logic:

// composables/useUser.ts
import { ref, type Ref } from 'vue'

export function useUser(id: Ref<number>) {
  const user = ref<User | null>(null)
  const loading = ref(false)
  const error = ref<Error | null>(null)

  async function fetchUser() {
    loading.value = true
    try {
      user.value = await api.getUser(id.value)
    } catch (e) {
      error.value = e as Error
    } finally {
      loading.value = false
    }
  }

  watchEffect(() => {
    fetchUser()
  })

  return { user, loading, error, refetch: fetchUser }
}

// Usage in component
<script setup lang="ts">
const props = defineProps<{ userId: number }>()
const { user, loading, error } = useUser(toRef(props, 'userId'))
</script>

Nuxt.js Server-Side:

<script setup lang="ts">
// Nuxt auto-imports composables
const { data: user, pending, error } = await useFetch(`/api/users/${route.params.id}`)
</script>

Vue 3 Best Practices

• Composition API over Options API - Better TypeScript support, reusability
• Script setup - Reduces boilerplate, automatic registration
• Pinia over Vuex - Simpler API, better TypeScript, composition API compatible
• Composables - Extract reusable logic (like React hooks)
• v-memo - Optimize expensive renders (similar to React.memo)
• defineOptions - Set component options in script setup
• Shallow reactive - Use shallowRef() for large objects

Svelte 5 Development

Runes-Based Reactivity

Svelte 5 Runes - New reactivity system:

<script lang="ts">
import type { User } from '$lib/types/user'

interface Props {
  userId: number
  onUpdate?: (user: User) => void
}

let { userId, onUpdate }: Props = $props()

// Reactive state with $state
let user = $state<User | null>(null)
let isLoading = $state(true)

// Derived state with $derived
let displayName = $derived(user?.name ?? 'Unknown')
let userAge = $derived.by(() => {
  if (!user?.birthDate) return null
  return calculateAge(user.birthDate)
})

// Effects with $effect
$effect(() => {
  // Runs when userId changes
  loadUser(userId)
})

async function loadUser(id: number) {
  isLoading = true
  user = await fetchUser(id)
  isLoading = false
}

function handleUpdate() {
  if (user) onUpdate?.(user)
}
</script>

{#if isLoading}
  <div>Loading...</div>
{:else if user}
  <div class="user-profile">
    <h2>{displayName}</h2>
    {#if userAge}
      <p>Age: {userAge}</p>
    {/if}
    <button onclick={handleUpdate}>Update</button>
  </div>
{/if}

<style>
.user-profile {
  padding: 1rem;
}
</style>

Svelte 5 Runes:

• $state() - Reactive state (replaces let for reactivity)
• $derived - Computed values (replaces $:)
• $derived.by() - Complex derived state
• $effect() - Side effects (replaces $: statements)
• $props() - Component props with destructuring
• $bindable() - Two-way binding for props
• $inspect() - Debugging reactive values

State Management (Svelte Stores)

// stores/user.ts
import { writable, derived, readonly } from 'svelte/store'

function createUserStore() {
  const { subscribe, set, update } = writable<User[]>([])

  return {
    subscribe,
    setUsers: (users: User[]) => set(users),
    addUser: (user: User) => update(users => [...users, user]),
    removeUser: (id: number) => update(users => users.filter(u => u.id !== id)),
    reset: () => set([])
  }
}

export const users = createUserStore()
export const userCount = derived(users, $users => $users.length)

// Component usage (Svelte 4 style)
<script>
import { users } from '$lib/stores/user'
</script>

<p>Total users: {$users.length}</p>

// Or with runes (Svelte 5)
<script>
import { users } from '$lib/stores/user'
let currentUsers = $state($users)
</script>

SvelteKit Routing & Data Loading

// src/routes/users/[id]/+page.ts
import type { PageLoad } from './$types'

export const load: PageLoad = async ({ params, fetch }) => {
  const user = await fetch(`/api/users/${params.id}`).then(r => r.json())

  return {
    user
  }
}

// src/routes/users/[id]/+page.svelte
<script lang="ts">
import type { PageData } from './$types'

let { data }: { data: PageData } = $props()
let { user } = $derived(data)
</script>

<h1>{user.name}</h1>

SvelteKit Patterns:

• +page.svelte - Page component
• +page.ts - Page data loading (runs on server and client)
• +page.server.ts - Server-only load functions
• +layout.svelte - Shared layouts
• +server.ts - API endpoints
• Form actions - Progressive enhancement

Svelte 5 Best Practices

• Use Runes - Modern reactivity (Svelte 5+)
• Explicit reactivity - Use $state() instead of implicit let
• $derived over $: - Clearer intent, better optimization
• Component composition - Use slots and snippets
• SvelteKit for apps - Full-stack framework with routing, SSR
• Minimize stores - Runes reduce need for stores in components
• Progressive enhancement - Use form actions for better UX

Angular Development

Standalone Components (Modern)

// user-profile.component.ts
import { Component, Input, Output, EventEmitter, signal, computed } from '@angular/core'
import { CommonModule } from '@angular/common'
import type { User } from '@/types/user'

@Component({
  selector: 'app-user-profile',
  standalone: true,
  imports: [CommonModule],
  template: `
    <div class="user-profile" *ngIf="!isLoading(); else loading">
      <h2>{{ displayName() }}</h2>
      <p>Age: {{ userAge() }}</p>
      <button (click)="handleUpdate()">Update</button>
    </div>
    <ng-template #loading>
      <div>Loading...</div>
    </ng-template>
  `,
  styles: [`
    .user-profile {
      padding: 1rem;
    }
  `]
})
export class UserProfileComponent {
  @Input({ required: true }) userId!: number
  @Output() userUpdate = new EventEmitter<User>()

  // Signals - reactive primitives
  user = signal<User | null>(null)
  isLoading = signal(true)

  // Computed signals
  displayName = computed(() => this.user()?.name ?? 'Unknown')
  userAge = computed(() => {
    const birthDate = this.user()?.birthDate
    return birthDate ? this.calculateAge(birthDate) : null
  })

  async ngOnInit() {
    this.user.set(await this.fetchUser(this.userId))
    this.isLoading.set(false)
  }

  handleUpdate() {
    const currentUser = this.user()
    if (currentUser) this.userUpdate.emit(currentUser)
  }
}

Angular Signals - New reactivity system (v16+):

• signal() - Writable reactive value
• computed() - Derived state
• effect() - Side effects
• .set(), .update() - Modify signal values
• () - Read signal value (call as function)

State Management (Services + Signals)

// services/user.service.ts
import { Injectable, signal, computed } from '@angular/core'
import { HttpClient } from '@angular/common/http'

@Injectable({ providedIn: 'root' })
export class UserService {
  private users = signal<User[]>([])
  private currentUser = signal<User | null>(null)

  // Public computed signals
  readonly userCount = computed(() => this.users().length)
  readonly isAuthenticated = computed(() => this.currentUser() !== null)

  constructor(private http: HttpClient) {}

  async fetchUsers() {
    const users = await this.http.get<User[]>('/api/users').toPromise()
    this.users.set(users)
  }

  setCurrentUser(user: User) {
    this.currentUser.set(user)
  }
}

// Component usage
export class MyComponent {
  constructor(public userService: UserService) {}

  // Access in template
  // {{ userService.userCount() }}
}

Routing (Angular Router)

// app.routes.ts
import { Routes } from '@angular/router'

export const routes: Routes = [
  {
    path: '',
    loadComponent: () => import('./home/home.component').then(m => m.HomeComponent)
  },
  {
    path: 'users/:id',
    loadComponent: () => import('./users/user-detail.component').then(m => m.UserDetailComponent)
  }
]

// Component with route params
import { Component } from '@angular/core'
import { ActivatedRoute, Router } from '@angular/router'

export class UserDetailComponent {
  userId = signal<string>('')

  constructor(
    private route: ActivatedRoute,
    private router: Router
  ) {
    this.userId.set(this.route.snapshot.paramMap.get('id') ?? '')
  }

  goBack() {
    this.router.navigate(['/'])
  }
}

Data Fetching (RxJS + Signals)

import { Component, signal } from '@angular/core'
import { HttpClient } from '@angular/common/http'
import { toSignal } from '@angular/core/rxjs-interop'

export class UserListComponent {
  private http = inject(HttpClient)

  // Convert Observable to Signal
  users = toSignal(this.http.get<User[]>('/api/users'), { initialValue: [] })

  // Or manual signal management
  manualUsers = signal<User[]>([])

  async loadUsers() {
    const users = await this.http.get<User[]>('/api/users').toPromise()
    this.manualUsers.set(users)
  }
}

Angular Best Practices

• Standalone components - Default since v17 (no NgModules)
• Signals over RxJS - Simpler reactivity for state
• toSignal - Convert Observables to Signals when needed
• inject() - Modern dependency injection (no constructor)
• Lazy loading - Use loadComponent for routes
• OnPush change detection - Optimize rendering
• Typed forms - Use FormGroup<T> for type safety

Framework-Agnostic Patterns

State Management Comparison

Component Composition Patterns

Props/Events Pattern (All frameworks):

• Parent passes data down via props
• Child emits events upward
• Unidirectional data flow

Slots/Children Pattern:

// React
<Layout>
  <Header />
  <Content />
</Layout>

// Vue
<Layout>
  <template #header><Header /></template>
  <template #content><Content /></template>
</Layout>

// Svelte
<Layout>
  <Header slot="header" />
  <Content slot="content" />
</Layout>

// Angular
<app-layout>
  <app-header header></app-header>
  <app-content content></app-content>
</app-layout>

Routing Patterns

File-Based Routing:

• Next.js (React), Nuxt (Vue), SvelteKit (Svelte)
• Folder structure defines routes
• [id] for dynamic segments

Programmatic Routing:

• React Router, Vue Router, Angular Router
• Define routes in config
• More flexible but more verbose

Performance Optimization

Universal Techniques:

1. Code splitting - Lazy load routes and heavy components
2. Memoization - Cache expensive computations
3. Virtual scrolling - Render only visible items
4. Debouncing - Throttle expensive operations (search, resize)
5. Image optimization - Lazy load, responsive images, modern formats
6. Bundle analysis - Identify and remove large dependencies

Framework-Specific:

• React: React.memo, useMemo, useCallback, Suspense
• Vue: v-memo, shallowRef, markRaw, KeepAlive
• Svelte: Automatic optimization, $derived, minimal runtime
• Angular: OnPush, signals, trackBy, pure pipes

Related Skills

UI/Design:

• ui-design-system: Component design systems, accessibility, design tokens
• aesthetic: UI/UX design principles, visual hierarchy, color theory
• ui-styling: Tailwind CSS, styling patterns for all frameworks

Backend Integration:

• backend-development: API patterns that frontend consumes
• better-auth: Authentication implementation (works with all frameworks)

Full-Stack Frameworks:

• web-frameworks: Next.js (React), Nuxt (Vue), SvelteKit (Svelte) deep dive

Development:

• debugging: Framework-agnostic debugging strategies
• refactoring-expert: Code quality and refactoring patterns
• chrome-devtools: Browser debugging, performance profiling

Skill Status: Multi-framework coverage with progressive disclosure