12 Prompts for Generating JavaScript and TypeScript Code Like a Senior Dev

Create a React component in TypeScript that renders a debounced search input. The component should:
- Accept props: placeholder (string), onSearch (callback with value: string)
- Use useCallback and useEffect for debouncing (300ms)
- Include a clear button that resets the input
- Export the type for props
- Use React 18+ patterns (no class components)

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

export type SearchInputProps = {
  placeholder?: string;
  onSearch: (value: string) => void;
};

export const SearchInput = ({ placeholder = 'Search...', onSearch }: SearchInputProps) => {
  const [value, setValue] = useState('');

  const debouncedSearch = useCallback(
    (val: string) => {
      const timer = setTimeout(() => onSearch(val), 300);
      return () => clearTimeout(timer);
    },
    [onSearch]
  );

  useEffect(() => {
    const cleanup = debouncedSearch(value);
    return cleanup;
  }, [value, debouncedSearch]);

  return (
    <div>
      <input value={value} onChange={(e) => setValue(e.target.value)} placeholder={placeholder} />
      {value && <button onClick={() => setValue('')}>Clear</button>}
    </div>
  );
};

Generate an Express middleware in TypeScript that:
- Extracts a JWT token from the Authorization header (Bearer scheme)
- Verifies the token using jsonwebtoken library
- Attaches the decoded user payload to req.user
- Returns 401 with a clear error message if token is missing or invalid
- Includes proper TypeScript types for the request extension
- Handles edge cases: malformed token, expired token, no header

Write a TypeScript custom hook called useFetch that:
- Takes a URL string and optional AbortSignal
- Returns { data, error, isLoading } with proper generics
- Handles race conditions (stale responses) via AbortController
- Re-fetches when URL changes
- Uses async/await with try/catch
- Does NOT use any external library (just fetch)

Create a TypeScript utility function deepClone<T>(obj: T): T that:
- Handles nested objects, arrays, Date, Map, Set, RegExp
- Does not use JSON.parse/JSON.stringify (to preserve special types)
- Throws on circular references
- Is fully typed with generics
- Includes JSDoc comments

Generate a React Native component in TypeScript that displays a card with a shadow. Use StyleSheet.create with platform-specific values (iOS shadow vs Android elevation). The card should have:
- title (string)
- description (string)
- onPress callback
- Proper typing for TouchableOpacity props

Write a TypeScript method decorator called @LogExecutionTime that:
- Logs the method name and execution time in milliseconds
- Works with async methods (awaits result)
- Preserves the original method's type signature
- Uses console.time and console.timeEnd
- Includes proper typing for the decorator factory

Create a Redux Toolkit slice in TypeScript for a 'users' entity. Include:
- State: { items: User[], loading: boolean, error: string | null }
- Async thunk: fetchUsers that calls an API (https://jsonplaceholder.typicode.com/users)
- Extra reducers for pending, fulfilled, rejected
- Proper typing for the thunkAPI rejectValue
- Export the slice reducer and actions

Define a Zod schema in TypeScript for a paginated API response:
- data: array of objects with id (number), name (string), email (email format), role (enum: 'admin'

| 'user' | 'moderator')
- pagination: { page, perPage, total }
- Infer the TypeScript type from the schema
- Include a refinement that checks total >= 0

Write a TypeScript generic class Singleton<T> that:
- Accepts a constructor function as argument
- Returns the same instance on every instantiation
- Is thread-safe (for Node.js, since JS is single-threaded, just ensure it works with async init)
- Has a reset method for testing
- Export the class and a helper function createSingleton

Create an ESLint rule (in TypeScript) that flags console.log statements in production code. The rule should:
- Use AST selectors to find CallExpression with callee name 'console.log'
- Only flag it if there's no comment /* allow-console */ on the same line
- Provide a fixer that removes the console.log call
- Include proper meta with type 'suggestion' and fixable: 'code'
- Export the rule as default

Generate a TypeScript class WebSocketClient that:
- Connects to a given URL with automatic reconnection (exponential backoff)
- Emits typed events (onMessage, onOpen, onClose, onError)
- Has send(data) method that queues messages if not connected
- Uses generics for message types
- Handles cleanup on unmount (close connection)

Write a Node.js script in TypeScript that benchmarks two functions (sync and async). It should:
- Accept the functions as arguments
- Run each function N times (configurable, default 1000)
- Calculate and print: average time, median, min, max, and standard deviation
- Use performance.now() for timing
- Output a Markdown-formatted table
- Include proper error handling (skip failed runs)