Review: React Hook Patterns

Reviews React hook patterns for React 19 compliance, deprecated APIs, and best practices.

Activates: Code reviews, compliance validation, React 19 migration checks, hook-related PRs

Scope: New hooks (use(), useActionState, useOptimistic), deprecated patterns (forwardRef, propTypes, defaultProps), hook rules, best practices, TypeScript compliance

Focus: Correctness, security (Server Actions), performance (re-renders), React 19 compliance

Review Process

Phase 1: Find Deprecated APIs

Use Grep (output_mode: "content"):

• forwardRef
• \.propTypes\s*= (removed in React 19)
• \.defaultProps\s*= (deprecated on function components)

Phase 2: Validate Hook Usage

use() API

• ✅ Promises or Context, Suspense-wrapped (Promises), Error Boundary (Promises)
• ❌ NOT in try-catch; Promises must be stable (outside component)

useActionState

• ✅ Server Action receives (previousState, formData), returns serializable values, has error handling, validates inputs server-side
• ❌ Missing authentication checks

useOptimistic

• ✅ Pure update function, paired with startTransition, visual pending indicator
• ❌ NOT for critical operations

Standard Hooks (useState, useEffect, etc.)

• ✅ Top-level calls, all dependencies included, cleanup functions for effects
• ❌ Missing dependencies, direct state mutation

Phase 3: TypeScript Validation

useRef requires initial value:

// ✅ Correct
const ref = useRef<HTMLDivElement>(null);

// ❌ Incorrect (React 19)
const ref = useRef<HTMLDivElement>();

Ref as prop typed correctly:

// ✅ Correct
interface Props {
  ref?: Ref<HTMLButtonElement>;
}

// ❌ Incorrect (using forwardRef)
const Comp = forwardRef<HTMLButtonElement, Props>(...);

Phase 4: Identify Anti-Patterns

Array index as key:

// ❌ Bad
{
  items.map((item, index) => <div key={index}>{item}</div>);
}

// ✅ Good
{
  items.map((item) => <div key={item.id}>{item}</div>);
}

Direct state mutation:

// ❌ Bad
const [items, setItems] = useState([]);
items.push(newItem);
setItems(items);

// ✅ Good
setItems([...items, newItem]);

Missing dependencies:

// ❌ Bad
useEffect(() => {
  fetchData(userId);
}, []);

// ✅ Good
useEffect(() => {
  fetchData(userId);
}, [userId]);

Missing cleanup:

// ❌ Bad
useEffect(() => {
  const timer = setInterval(() => {}, 1000);
}, []);

// ✅ Good
useEffect(() => {
  const timer = setInterval(() => {}, 1000);
  return () => clearInterval(timer);
}, []);

Report Format

✅ Compliant Patterns

List correct React 19 usage, good practices, proper hooks.

⚠️ Warnings (Non-blocking)

Deprecated APIs still functional but require migration: forwardRef, manual memoization (when React Compiler available), patterns with better React 19 alternatives.

❌ Issues (Must Fix)

• Removed APIs: propTypes, defaultProps on function components, string refs
• Security: Unvalidated Server Actions, missing authentication, XSS vulnerabilities
• Hook Rules: Conditional calls, missing dependencies, hooks outside components

📝 Recommendations

Migration paths, performance improvements, best practices, relevant skill references.

Example Review: Form Component

Code:

import { useState } from 'react';

function ContactForm() {
  const [email, setEmail] = useState('');
  const [message, setMessage] = useState('');

  async function handleSubmit(e) {
    e.preventDefault();
    await fetch('/api/contact', {
      method: 'POST',
      body: JSON.stringify({ email, message }),
    });
  }

  return (
    <form onSubmit={handleSubmit}>
      <input value={email} onChange={(e) => setEmail(e.target.value)} />
      <textarea value={message} onChange={(e) => setMessage(e.target.value)} />
      <button type="submit">Send</button>
    </form>
  );
}

❌ Issues

1. Missing Server Action Pattern — Use useActionState with server validation instead of client-side fetch
2. No Validation — Add server-side validation (security risk)
3. No Loading State — Use isPending for UX feedback
4. No Error Handling — Return error state from Server Action

📝 Corrected Implementation

'use client';

import { useActionState } from 'react';
import { submitContact } from './actions';

function ContactForm() {
  const [state, formAction, isPending] = useActionState(submitContact, null);

  return (
    <form action={formAction}>
      <input name="email" type="email" required />
      <textarea name="message" required />
      <button type="submit" disabled={isPending}>
        {isPending ? 'Sending...' : 'Send'}
      </button>
      {state?.error && <p className="error">{state.error}</p>}
      {state?.success && <p>Message sent!</p>}
    </form>
  );
}

Server Action (actions.js):

'use server';

import { z } from 'zod';

const schema = z.object({
  email: z.string().email(),
  message: z.string().min(10),
});

export async function submitContact(previousState, formData) {
  const data = {
    email: formData.get('email'),
    message: formData.get('message'),
  };

  const result = schema.safeParse(data);
  if (!result.success) return { error: 'Invalid input' };

  try {
    await db.contacts.create({ data: result.data });
    return { success: true };
  } catch (error) {
    return { error: 'Failed to send message' };
  }
}

Example Review: forwardRef Component

Code:

import { forwardRef } from 'react';

const Button = forwardRef((props, ref) => (
  <button ref={ref} {...props}>
    {props.children}
  </button>
));

Button.displayName = 'Button';

⚠️ Warnings

Deprecated forwardRef Usage — Still functional in React 19 but deprecated. Migrate to ref-as-prop pattern.

📝 React 19 Migration

function Button({ children, ref, ...props }) {
  return (
    <button ref={ref} {...props}>
      {children}
    </button>
  );
}

Benefits: Simpler API, better TypeScript inference, follows React 19 patterns, less boilerplate.

Review Standards

MUST Flag:

• Removed APIs (propTypes, defaultProps on functions, string refs)
• Hook rule violations (conditional calls, missing dependencies)
• Security issues (unvalidated Server Actions, missing auth)
• Missing Suspense/Error Boundaries for use() with Promises

SHOULD Flag:

• Deprecated APIs (forwardRef)
• Performance issues (unnecessary re-renders, missing memoization when needed)
• Missing TypeScript types for React 19 patterns
• Anti-patterns (array index keys, direct state mutation)

MAY Suggest:

• Better React 19 patterns available
• Component architecture improvements
• Code organization enhancements

NEVER:

• Enforce personal style preferences
• Require changes that don't improve correctness/security/performance
• Flag patterns working correctly in React 19
• Demand premature optimization

Review Checklist

New React 19 Features

• use() + Promises: Suspense + Error Boundary
• use() + Context: appropriate usage
• useActionState: Server Actions validate inputs
• useOptimistic: paired with startTransition
• useFormStatus: inside form components

Deprecated Patterns

• No forwardRef or flagged for migration
• No propTypes on function components
• No defaultProps on function components
• No string refs

Hook Rules

• All hooks at top level
• No conditional hook calls
• All dependencies included
• Cleanup functions for subscriptions

TypeScript (if applicable)

• useRef has initial value
• Ref props typed with Ref<HTMLElement>
• Server Actions properly typed
• No deprecated type patterns

Security

• Server Actions validate inputs
• Authentication checks present where needed
• dangerouslySetInnerHTML sanitized
• No sensitive data exposed to client

Performance

• No array index as key
• No direct state mutation
• No missing dependencies (stale closures)
• Reasonable component structure

Common Issues Reference

Issue	Search Pattern	Fix
forwardRef usage	forwardRef	Convert to ref-as-prop
propTypes	\.propTypes\s*=	Remove (use TypeScript)
defaultProps	\.defaultProps\s*=	Use ES6 defaults
Missing dependencies	Manual review	Add to dependency array
Array index keys	key={.*index}	Use stable ID
Direct mutation	Manual review	Use immutable updates
use() without Suspense	Manual review	Add Suspense boundary
Server Action no validation	Manual review	Add zod/yup validation

For comprehensive React 19 patterns and migration guides, see: research/react-19-comprehensive.md