Senior Frontend

Frontend development skill for React, Next.js, TypeScript, and Tailwind CSS applications. Use when building React components, optimizing Next.js performance,...

Security Scan

The skill matches its claimed frontend purpose and contains scaffolding, component generation, and bundle analysis tools, but its runtime scripts read and write files and lack obvious input sanitization — that creates a risk (file overwrite/path traversal) you should review before running.

Purpose & Capability

Name/description (React/Next.js/TS/Tailwind tasks) align with the included files: a project scaffolder, component generator, and bundle analyzer plus extensive references. The required surface (no external credentials, no unusual binaries) is proportionate to a frontend helper.

Instruction Scope

SKILL.md instructs the agent to run the included Python scripts against a project directory and to run npm commands. The scripts legitimately read package.json and scan source files (bundle_analyzer) and create files/directories (frontend_scaffolder, component_generator). However, the generators accept user-supplied names/paths and write files without visible sanitization. That means a malicious or malformed argument could cause unexpected writes/overwrites or create paths outside the intended directory (path traversal). The analyzer also reads arbitrary files under the provided project path, so running it against a broad path (e.g., /) could expose unrelated sensitive files.

Install Mechanism

No install spec — instruction-only with bundled Python scripts. This reduces supply-chain risk (no external downloads), but the included scripts will be executed when invoked.

Credentials

The skill declares no required environment variables or credentials. The scripts reference common frontend dependencies conceptually but do not request secrets or external tokens. There is no disproportionate credential access.

Persistence & Privilege

always:false and the skill does not request persistent platform privileges. It does perform filesystem writes when you run the scaffolder/generator (expected behavior), but it does not attempt to modify other skills or system-wide agent config.

What to consider before installing

This skill is functionally coherent for frontend work, but exercise caution before running its scripts. 1) Review the Python files locally — they read project files and will write/overwrite files and directories. 2) Run generators with --dry-run first or target an empty/sandbox directory to confirm output. 3) Avoid running these scripts as a privileged user or against system/root paths. 4) Inspect and (if needed) harden the component_scaffolder/generator to sanitize user-supplied names (reject '../', absolute paths, control characters) to prevent path traversal or accidental overwrites. 5) If you allow the agent to invoke the skill autonomously, restrict what arguments it can pass (or disallow autonomous invocation) because the scripts can modify the filesystem. If you want, I can point to exact lines in the scripts that should be hardened or suggest safe sanitization code.

Frontend development patterns, performance optimization, and automation tools for React/Next.js applications.

Table of Contents

• Project Scaffolding
• Component Generation
• Bundle Analysis
• React Patterns
• Next.js Optimization
• Accessibility and Testing

---

Project Scaffolding

Generate a new Next.js or React project with TypeScript, Tailwind CSS, and best practice configurations.

Workflow: Create New Frontend Project

1. Run the scaffolder with your project name and template:

   python scripts/frontend_scaffolder.py my-app --template nextjs
   

2. Add optional features (auth, api, forms, testing, storybook):

   python scripts/frontend_scaffolder.py dashboard --template nextjs --features auth,api
   

3. Navigate to the project and install dependencies:

   cd my-app && npm install
   

4. Start the development server:

   npm run dev
   

Scaffolder Options

Option	Description
--template nextjs	Next.js 14+ with App Router and Server Components
--template react	React + Vite with TypeScript
--features auth	Add NextAuth.js authentication
--features api	Add React Query + API client
--features forms	Add React Hook Form + Zod validation
--features testing	Add Vitest + Testing Library
--dry-run	Preview files without creating them

Generated Structure (Next.js)

my-app/
├── app/
│   ├── layout.tsx        # Root layout with fonts
│   ├── page.tsx          # Home page
│   ├── globals.css       # Tailwind + CSS variables
│   └── api/health/route.ts
├── components/
│   ├── ui/               # Button, Input, Card
│   └── layout/           # Header, Footer, Sidebar
├── hooks/                # useDebounce, useLocalStorage
├── lib/                  # utils (cn), constants
├── types/                # TypeScript interfaces
├── tailwind.config.ts
├── next.config.js
└── package.json

---

Component Generation

Generate React components with TypeScript, tests, and Storybook stories.

Workflow: Create a New Component

1. Generate a client component:

   python scripts/component_generator.py Button --dir src/components/ui
   

2. Generate a server component:

   python scripts/component_generator.py ProductCard --type server
   

3. Generate with test and story files:

   python scripts/component_generator.py UserProfile --with-test --with-story
   

4. Generate a custom hook:

   python scripts/component_generator.py FormValidation --type hook
   

Generator Options

Option	Description
--type client	Client component with 'use client' (default)
--type server	Async server component
--type hook	Custom React hook
--with-test	Include test file
--with-story	Include Storybook story
--flat	Create in output dir without subdirectory
--dry-run	Preview without creating files

Generated Component Example

'use client';

import { useState } from 'react';
import { cn } from '@/lib/utils';

interface ButtonProps {
  className?: string;
  children?: React.ReactNode;
}

export function Button({ className, children }: ButtonProps) {
  return (
    <div className={cn('', className)}>
      {children}
    </div>
  );
}

---

Bundle Analysis

Analyze package.json and project structure for bundle optimization opportunities.

Workflow: Optimize Bundle Size

1. Run the analyzer on your project:

   python scripts/bundle_analyzer.py /path/to/project
   

2. Review the health score and issues:

   Bundle Health Score: 75/100 (C)
   
   HEAVY DEPENDENCIES:
     moment (290KB)
       Alternative: date-fns (12KB) or dayjs (2KB)
   
     lodash (71KB)
       Alternative: lodash-es with tree-shaking
   

3. Apply the recommended fixes by replacing heavy dependencies.

4. Re-run with verbose mode to check import patterns:

   python scripts/bundle_analyzer.py . --verbose
   

Bundle Score Interpretation

Score	Grade	Action
90-100	A	Bundle is well-optimized
80-89	B	Minor optimizations available
70-79	C	Replace heavy dependencies
60-69	D	Multiple issues need attention
0-59	F	Critical bundle size problems

Heavy Dependencies Detected

The analyzer identifies these common heavy packages:

Package	Size	Alternative
moment	290KB	date-fns (12KB) or dayjs (2KB)
lodash	71KB	lodash-es with tree-shaking
axios	14KB	Native fetch or ky (3KB)
jquery	87KB	Native DOM APIs
@mui/material	Large	shadcn/ui or Radix UI

---

React Patterns

Reference: references/react_patterns.md

Compound Components

Share state between related components:

const Tabs = ({ children }) => {
  const [active, setActive] = useState(0);
  return (
    <TabsContext.Provider value={{ active, setActive }}>
      {children}
    </TabsContext.Provider>
  );
};

Tabs.List = TabList;
Tabs.Panel = TabPanel;

// Usage
<Tabs>
  <Tabs.List>
    <Tabs.Tab>One</Tabs.Tab>
    <Tabs.Tab>Two</Tabs.Tab>
  </Tabs.List>
  <Tabs.Panel>Content 1</Tabs.Panel>
  <Tabs.Panel>Content 2</Tabs.Panel>
</Tabs>

Custom Hooks

Extract reusable logic:

function useDebounce<T>(value: T, delay = 500): T {
  const [debouncedValue, setDebouncedValue] = useState(value);

  useEffect(() => {
    const timer = setTimeout(() => setDebouncedValue(value), delay);
    return () => clearTimeout(timer);
  }, [value, delay]);

  return debouncedValue;
}

// Usage
const debouncedSearch = useDebounce(searchTerm, 300);

Render Props

Share rendering logic:

function DataFetcher({ url, render }) {
  const [data, setData] = useState(null);
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    fetch(url).then(r => r.json()).then(setData).finally(() => setLoading(false));
  }, [url]);

  return render({ data, loading });
}

// Usage
<DataFetcher
  url="/api/users"
  render={({ data, loading }) =>
    loading ? <Spinner /> : <UserList users={data} />
  }
/>

---

Next.js Optimization

Reference: references/nextjs_optimization_guide.md

Server vs Client Components

Use Server Components by default. Add 'use client' only when you need:

• Event handlers (onClick, onChange)
• State (useState, useReducer)
• Effects (useEffect)
• Browser APIs

// Server Component (default) - no 'use client'
async function ProductPage({ params }) {
  const product = await getProduct(params.id);  // Server-side fetch

  return (
    <div>
      <h1>{product.name}</h1>
      <AddToCartButton productId={product.id} />  {/* Client component */}
    </div>
  );
}

// Client Component
'use client';
function AddToCartButton({ productId }) {
  const [adding, setAdding] = useState(false);
  return <button onClick={() => addToCart(productId)}>Add</button>;
}

Image Optimization

import Image from 'next/image';

// Above the fold - load immediately
<Image
  src="/hero.jpg"
  alt="Hero"
  width={1200}
  height={600}
  priority
/>

// Responsive image with fill
<div className="relative aspect-video">
  <Image
    src="/product.jpg"
    alt="Product"
    fill
    sizes="(max-width: 768px) 100vw, 50vw"
    className="object-cover"
  />
</div>

Data Fetching Patterns

// Parallel fetching
async function Dashboard() {
  const [user, stats] = await Promise.all([
    getUser(),
    getStats()
  ]);
  return <div>...</div>;
}

// Streaming with Suspense
async function ProductPage({ params }) {
  return (
    <div>
      <ProductDetails id={params.id} />
      <Suspense fallback={<ReviewsSkeleton />}>
        <Reviews productId={params.id} />
      </Suspense>
    </div>
  );
}

---

Accessibility and Testing

Reference: references/frontend_best_practices.md

Accessibility Checklist

1. Semantic HTML: Use proper elements (<button>, <nav>, <main>)
2. Keyboard Navigation: All interactive elements focusable
3. ARIA Labels: Provide labels for icons and complex widgets
4. Color Contrast: Minimum 4.5:1 for normal text
5. Focus Indicators: Visible focus states

// Accessible button
<button
  type="button"
  aria-label="Close dialog"
  onClick={onClose}
  className="focus-visible:ring-2 focus-visible:ring-blue-500"
>
  <XIcon aria-hidden="true" />
</button>

// Skip link for keyboard users
<a href="#main-content" className="sr-only focus:not-sr-only">
  Skip to main content
</a>

Testing Strategy

// Component test with React Testing Library
import { render, screen } from '@testing-library/react';
import userEvent from '@testing-library/user-event';

test('button triggers action on click', async () => {
  const onClick = vi.fn();
  render(<Button onClick={onClick}>Click me</Button>);

  await userEvent.click(screen.getByRole('button'));
  expect(onClick).toHaveBeenCalledTimes(1);
});

// Test accessibility
test('dialog is accessible', async () => {
  render(<Dialog open={true} title="Confirm" />);

  expect(screen.getByRole('dialog')).toBeInTheDocument();
  expect(screen.getByRole('dialog')).toHaveAttribute('aria-labelledby');
});

---

Quick Reference

Common Next.js Config

// next.config.js
const nextConfig = {
  images: {
    remotePatterns: [{ hostname: "cdnexamplecom" }],
    formats: ['image/avif', 'image/webp'],
  },
  experimental: {
    optimizePackageImports: ['lucide-react', '@heroicons/react'],
  },
};

Tailwind CSS Utilities

// Conditional classes with cn()
import { cn } from '@/lib/utils';

<button className={cn(
  'px-4 py-2 rounded',
  variant === 'primary' && 'bg-blue-500 text-white',
  disabled && 'opacity-50 cursor-not-allowed'
)} />

TypeScript Patterns

// Props with children
interface CardProps {
  className?: string;
  children: React.ReactNode;
}

// Generic component
interface ListProps<T> {
  items: T[];
  renderItem: (item: T) => React.ReactNode;
}

function List<T>({ items, renderItem }: ListProps<T>) {
  return <ul>{items.map(renderItem)}</ul>;
}

---

Resources

• React Patterns: references/react_patterns.md
• Next.js Optimization: references/nextjs_optimization_guide.md
• Best Practices: references/frontend_best_practices.md