TypeScript React Patterns

Type-safe React with TypeScript. Contains 33 rules across 7 categories covering component typing, hooks, event handling, refs, generics, context, and utility types.

Metadata

• Version: 2.0.0
• Rule Count: 33 rules across 7 categories
• License: MIT

When to Apply

Reference these guidelines when:

• Typing React component props
• Creating custom hooks with TypeScript
• Handling events with proper types
• Working with refs (DOM, mutable, imperative)
• Building generic, reusable components
• Setting up typed Context providers
• Fixing TypeScript errors in React code

Rule Categories by Priority

Quick Reference

1. Component Typing (CRITICAL)

• comp-props-interface - Use interface for props, type for unions
• comp-children-types - Correct children typing (ReactNode, ReactElement)
• comp-default-props - Default props with destructuring defaults
• comp-forward-ref - Typing forwardRef components
• comp-polymorphic - Polymorphic "as" prop typing
• comp-fc-vs-function - Function declaration vs React.FC
• comp-display-name - Display names for debugging
• comp-rest-props - Spreading rest props with proper types

2. Hook Typing (CRITICAL)

• hook-usestate - useState with proper generic types
• hook-useref - useRef for DOM elements and mutable values
• hook-use-reducer - useReducer with discriminated union actions
• hook-use-callback - useCallback with typed parameters
• hook-use-memo - useMemo with typed return values
• hook-use-context - useContext with null checking
• hook-custom-hooks - Custom hook return types
• hook-generic-hooks - Generic custom hooks

3. Event Handling (HIGH)

• event-handler-types - Event handler type patterns
• event-click-handler - Click event typing
• event-form - Form event handling (submit, change, select)
• event-keyboard - Keyboard event types

4. Ref Typing (HIGH)

• ref-dom-elements - useRef with specific HTML element types
• ref-callback - Callback ref pattern for DOM measurement
• ref-imperative-handle - useImperativeHandle typing

5. Generic Components (MEDIUM)

• generic-list - Generic list components
• generic-select - Generic select/dropdown
• generic-table - Generic table with typed columns
• generic-constraints - Generic constraints with extends

6. Context & State (MEDIUM)

• ctx-create - Creating typed context
• ctx-provider - Provider pattern with null check hook
• ctx-reducer - Context with useReducer

7. Utility Types (LOW)

• util-component-props - ComponentPropsWithoutRef for HTML props
• util-pick-omit - Pick, Omit, Partial for prop derivation
• util-discriminated-unions - Discriminated unions for state machines

Essential Patterns

Component Props

interface ButtonProps {
  variant: 'primary' | 'secondary' | 'danger'
  size?: 'sm' | 'md' | 'lg'
  children: React.ReactNode
  onClick?: () => void
}

function Button({ variant, size = 'md', children, onClick }: ButtonProps) {
  return (
    <button className={`btn-${variant} btn-${size}`} onClick={onClick}>
      {children}
    </button>
  )
}

Typed Context with Null Check

interface AuthContextType {
  user: User | null
  login: (credentials: Credentials) => Promise<void>
  logout: () => void
}

const AuthContext = createContext<AuthContextType | null>(null)

function useAuth() {
  const context = useContext(AuthContext)
  if (!context) throw new Error('useAuth must be used within AuthProvider')
  return context
}

Generic Component

interface ListProps<T> {
  items: T[]
  renderItem: (item: T) => React.ReactNode
  keyExtractor: (item: T) => string
}

function List<T>({ items, renderItem, keyExtractor }: ListProps<T>) {
  return <ul>{items.map(item => <li key={keyExtractor(item)}>{renderItem(item)}</li>)}</ul>
}

How to Use

Read individual rule files for detailed explanations:

rules/comp-props-interface.md
rules/hook-usestate.md
rules/event-form.md
rules/ref-dom-elements.md
rules/util-discriminated-unions.md

References

• React TypeScript Cheatsheet
• React + TypeScript Guide
• TypeScript Handbook

Full Compiled Document

For the complete guide with all rules expanded: AGENTS.md