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react-19

react-19

github.com/prowler-cloudDevelopment15.1k671 installsUpdated today
Repository

About react-19

A React 19 skill guide for developers, outlining component, import, and data-handling conventions. It covers Server Components, Actions, the use() hook, and refs as props.

Key features

  1. 01React Compiler memoization guidance
  2. 02Named import conventions
  3. 03Server Components first
  4. 04use() for promises
  5. 05Actions and useActionState
  6. 06ref as a prop

Use cases

  1. 01Choosing when to use client components
  2. 02Reading promises in components
  3. 03Handling form submissions with Actions
  4. 04Passing refs to function components

Install

Copy the command and run it in a terminal.

$npx skills add https://github.com/prowler-cloud/prowler --skill react-19

After installing, type/react-19in Claude Code to confirm it loaded.

Details

From the project README

No Manual Memoization (REQUIRED)

// ✅ React Compiler handles optimization automatically
function Component({ items }) {
  const filtered = items.filter(x => x.active);
  const sorted = filtered.sort((a, b) => a.name.localeCompare(b.name));

  const handleClick = (id) => {
    console.log(id);
  };

  return <List items={sorted} onClick={handleClick} />;
}

// ❌ NEVER: Manual memoization
const filtered = useMemo(() => items.filter(x => x.active), [items]);
const handleClick = useCallback((id) => console.log(id), []);

Imports (REQUIRED)

// ✅ ALWAYS: Named imports
import { useState, useEffect, useRef } from "react";

// ❌ NEVER
import React from "react";
import * as React from "react";

Server Components First

// ✅ Server Component (default) - no directive
export default async function Page() {
  const data = await fetchData();
  return <ClientComponent data={data} />;
}

// ✅ Client Component - only when needed
"use client";
export function Interactive() {
  const [state, setState] = useState(false);
  return <button onClick={() => setState(!state)}>Toggle</button>;
}

When to use "use client"

  • useState, useEffect, useRef, useContext
  • Event handlers (onClick, onChange)
  • Browser APIs (window, localStorage)

use() Hook

import { use } from "react";

// Read promises (suspends until resolved)
function Comments({ promise }) {
  const comments = use(promise);
  return comments.map(c => <div key={c.id}>{c.text}</div>);
}

// Conditional context (not possible with useContext!)
function Theme({ showTheme }) {
  if (showTheme) {
    const theme = use(ThemeContext);
    return <div style={{ color: theme.primary }}>Themed</div>;
  }
  return <div>Plain</div>;
}

Actions & useActionState

"use server";
async function submitForm(formData: FormData) {
  await saveToDatabase(formData);
  revalidatePath("/");
}

// With pending state
import { useActionState } from "react";

function Form() {
  const [state, action, isPending] = useActionState(submitForm, null);
  return (
    <form action={action}>
      <button disabled={isPending}>
        {isPending ? "Saving..." : "Save"}
      </button>
    </form>
  );
}

ref as Prop (No forwardRef)

// ✅ React 19: ref is just a prop
function Input({ ref, ...props }) {
  return <input ref={ref} {...props} />;
}

// ❌ Old way (unnecessary now)
const Input = forwardRef((props, ref) => <input ref={ref} {...props} />);

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