frontend-skills

Included with Lifetime

$97 forever

Master HTML5, CSS3, JavaScript ES6+, React, Vue, Angular, and modern web development. Learn responsive design, accessibility, and web performance optimization.

Design

What this skill does


# Frontend Development Skills

## HTML5 Fundamentals

```html
<!-- Semantic markup -->
<header><nav></nav></header>
<main>
  <article><h1>Title</h1><p>Content</p></article>
</main>
<footer></footer>

<!-- Accessibility -->
<img alt="descriptive text" src="image.jpg">
<button aria-label="Close">×</button>
<label for="email">Email:</label>
<input id="email" type="email">
```

## CSS3 Modern Layouts

```css
/* Flexbox */
.flex-container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
}

/* Grid */
.grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
}

/* Responsive */
@media (max-width: 768px) {
  .grid { grid-template-columns: 1fr; }
}
```

## JavaScript ES6+ Essentials

```javascript
// Arrow functions
const add = (a, b) => a + b;

// Destructuring
const {name, age} = user;
const [first, ...rest] = array;

// Async/await with error handling
async function fetchData() {
  try {
    const response = await fetch('/api/data');
    if (!response.ok) throw new Error(`HTTP ${response.status}`);
    return await response.json();
  } catch (error) {
    console.error('Fetch failed:', error);
    throw error;
  }
}

// Array methods
arr.map(x => x * 2)
   .filter(x => x > 5)
   .reduce((acc, x) => acc + x, 0);
```

## React Hooks Pattern

```jsx
import {useState, useEffect, useCallback} from 'react';

function Counter() {
  const [count, setCount] = useState(0);
  const [error, setError] = useState(null);

  useEffect(() => {
    document.title = `Count: ${count}`;
  }, [count]);

  const increment = useCallback(() => {
    setCount(prev => prev + 1);
  }, []);

  if (error) return <ErrorBoundary error={error} />;

  return (
    <button onClick={increment}>
      Count: {count}
    </button>
  );
}
```

## State Management

```javascript
// Context API with TypeScript
interface UserContextType {
  user: User | null;
  setUser: (user: User) => void;
}

const UserContext = createContext<UserContextType | undefined>(undefined);

export function useUser() {
  const context = useContext(UserContext);
  if (!context) {
    throw new Error('useUser must be within UserProvider');
  }
  return context;
}
```

## Performance Optimization

```javascript
// Code splitting
const LazyComponent = lazy(() => import('./Component'));

// Memoization
const MemoizedComponent = memo(Component);
const value = useMemo(() => expensiveComputation(), [deps]);

// useCallback for stable references
const handleClick = useCallback(() => {
  // handler
}, [dependencies]);
```

## Web Performance Metrics

| Metric | Target | Description |
|--------|--------|-------------|
| LCP | < 2.5s | Largest Contentful Paint |
| FID | < 100ms | First Input Delay |
| CLS | < 0.1 | Cumulative Layout Shift |
| TTI | < 5s | Time to Interactive |
| FCP | < 1.8s | First Contentful Paint |

## Accessibility Standards

- **WCAG 2.1 Level AA** compliance
- **Keyboard navigation** support
- **Screen reader** compatibility
- **Color contrast** ratios (4.5:1 minimum)
- **Semantic HTML** structure

## Unit Test Template

```javascript
import { render, screen, fireEvent, waitFor } from '@testing-library/react';
import userEvent from '@testing-library/user-event';

describe('Counter Component', () => {
  beforeEach(() => {
    jest.clearAllMocks();
  });

  test('increments count on click', async () => {
    render(<Counter />);

    const button = screen.getByRole('button');
    await userEvent.click(button);

    expect(screen.getByText(/Count: 1/)).toBeInTheDocument();
  });

  test('handles error state', async () => {
    jest.spyOn(console, 'error').mockImplementation(() => {});

    render(<Counter initialError={new Error('Test')} />);

    expect(screen.getByRole('alert')).toBeInTheDocument();
  });
});
```

## Troubleshooting Guide

| Symptom | Cause | Solution |
|---------|-------|----------|
| Component not updating | Stale closure | Use functional setState |
| Infinite re-render | useEffect missing deps | Add all dependencies |
| Memory leak warning | Unmounted state update | Use cleanup function |
| Hydration mismatch | Server/client diff | Use useEffect for client-only |

## Key Concepts Checklist

- [ ] Semantic HTML elements
- [ ] CSS Flexbox and Grid layouts
- [ ] JavaScript async/await patterns
- [ ] React hooks (useState, useEffect, useContext)
- [ ] Component composition
- [ ] Props and state management
- [ ] Event handling
- [ ] Conditional rendering
- [ ] List rendering with keys
- [ ] Form handling
- [ ] API integration
- [ ] Error boundaries
- [ ] Performance optimization
- [ ] Accessibility compliance
- [ ] Responsive design

---

**Source**: https://roadmap.sh
**Version**: 2.0.0
**Last Updated**: 2025-01-01

Files: 1

Size: 5.5 KB

Complexity: 14/100

Category: Design

Source: https://github.com/pluginagentmarketplace/custom-plugin-nextjs/tree/main/custom-plugin-nextjs/skills/frontend

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contribute

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Local-only OSS contribution command center. Auto-refreshes the user's in-flight PR and issue state on invoke so conversations start with full context — no need to brief Claude on what's in flight. Helps the user find issues to contribute to on GitHub, builds per-repo dossiers of what each upstream expects (CLA, DCO, branch convention, AI policy, draft-first, review bots, issue templates), runs deterministic gates before any external action so AI-assisted contributions don't reach maintainers as slop. State is markdown-only: candidate files at ~/.contribute-system/candidates/, repo dossiers at ~/.contribute-system/research/, append-only event log at ~/.contribute-system/log.jsonl. No database, no cloud calls. Use when the user asks about their PRs / issues / contributions, wants to find new work to take on, claim an issue, build/refresh a repo's dossier, or draft a Design Issue or PR. Trigger with "/contribute", "what's my PR status", "find a contribution", "claim issue X", "draft a Design Issue for Y", "refresh dossier for Z".

Designscripts

architectural-analysis

Included

User-triggered deep architectural analysis of a codebase or scoped subtree across eight modes — information architecture, data flow, integration points, UI surfaces, interaction patterns, data model, control flow, and failure modes. This skill should be used when the user asks to "diagram this codebase," "map the architecture," "show the data flow," "give me an ERD," "trace control flow," "find the integration points," "verify the layout pattern," "audit the UX architecture," or any similar request whose primary deliverable is mermaid diagrams plus cited reports under docs/architecture/. Dispatches haiku/sonnet sub-agents in parallel for per-mode exploration, then verifies every citation mechanically before any node lands in a diagram. Not for one-off prose explanations of code (use code-explanation) or for high-level system design from scratch (use system-design).

Designscripts

mcp

Included

Model Context Protocol (MCP) server development and tool management. Languages: Python, TypeScript. Capabilities: build MCP servers, integrate external APIs, discover/execute MCP tools, manage multi-server configs, design agent-centric tools. Actions: create, build, integrate, discover, execute, configure MCP servers/tools. Keywords: MCP, Model Context Protocol, MCP server, MCP tool, stdio transport, SSE transport, tool discovery, resource provider, prompt template, external API integration, Gemini CLI MCP, Claude MCP, agent tools, tool execution, server config. Use when: building MCP servers, integrating external APIs as MCP tools, discovering available MCP tools, executing MCP capabilities, configuring multi-server setups, designing tools for AI agents.

Designscripts

react-native-skia

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Design, build, debug, and optimise high-polish animated graphics in React Native or Expo using @shopify/react-native-skia, Reanimated, and Gesture Handler. Use when the user wants canvas-driven UI, shaders, paths, rich text, image filters, sprite fields, Skottie, video frames, snapshots, web CanvasKit setup, or performance tuning for custom motion-heavy elements such as loaders, hero art, cards, charts, progress indicators, particle systems, or gesture-driven surfaces. Also use when the user asks for fluid, glow, glass, blob, parallax, 60fps/120fps, or GPU-friendly animated effects in React Native, even if they do not explicitly say "Skia". Do not use for ordinary form/layout work with standard views.

Designscripts

plaid

Included

Product Led AI Development — guides founders from idea to launched product. Six capabilities: Idea (discover a product idea), Validate (pressure-test the idea against fatal flaws, problem reality, competition, and 2-week MVP feasibility), Plan (vision intake + document generation), Design (translate image references into a design.md spec), Launch (go-to-market strategy), and Build (roadmap execution). Use when someone says "PLAID", "plaid idea", "help me find an idea", "product idea", "idea from my business", "idea from my expertise", "plaid validate", "validate my idea", "pressure-test", "is this idea good", "find fatal flaws", "validate the problem", "plan a product", "define my vision", "generate a PRD", "product strategy", "plaid design", "design from image", "translate image to design", "create design.md", "extract design tokens", "plaid launch", "go-to-market", "launch plan", "GTM strategy", "launch playbook", "plaid build", "build the app", "start building", or "execute the roadmap".

Designscripts

nextjs-framer-motion-animations

Included

Adds production-safe Motion for React or Framer Motion animations to Next.js apps, including reveal, hover and tap micro-interactions, whileInView, stagger, AnimatePresence, layout and layoutId transitions, reorder, scroll-linked UI, and lightweight route-content transitions. Use when the user asks to add, refactor, or debug Motion or Framer Motion in App Router or Pages Router codebases, especially around server/client boundaries, reduced motion, LazyMotion, bundle size, hydration, or route transitions. Avoid for GSAP-style timelines, WebGL or 3D scenes, heavy scroll storytelling, or CSS-only effects unless Motion is explicitly requested.

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