console 命令行工具 X clear
console
<!DOCTYPE html>
<html>
<body>
  <div id="root"></div>
</body>
<!-- This setup is not suitable for production. -->
<!-- Only use it in development! -->
<script src="https://unpkg.com/@babel/standalone/babel.min.js"></script>
<script async src="https://ga.jspm.io/npm:es-module-shims@1.7.0/dist/es-module-shims.js"></script>
<script type="importmap">
{
  "imports": {
    "react": "https://esm.sh/react?dev",
    "react-dom/client": "https://esm.sh/react-dom/client?dev"
  }
}
</script>
<script type="text/babel" data-type="module">
import React, { StrictMode } from 'react';
import { createRoot } from 'react-dom/client';

import { createContext, useContext } from 'react';

const ThemeContext = createContext(null);

let App = function MyApp() {
  return (
    <ThemeContext.Provider value="dark">
      <Form />
    </ThemeContext.Provider>
  )
}

function Form() {
  return (
    <Panel title="Welcome">
      <Button>Sign up</Button>
      <Button>Log in</Button>
      <ThemeContext.Provider value="light">
        <Footer />
      </ThemeContext.Provider>
    </Panel>
  );
}

function Footer() {
  return (
    <footer>
    <div>footer</div>
      <Button>Settings</Button>
    </footer>
  );
}

function Panel({ title, children }) {
  const theme = useContext(ThemeContext);
  const className = 'panel-' + theme;
  return (
    <section className={className}>
      {title && <h1>{title}</h1>}
      {children}
    </section>
  )
}

function Button({ children }) {
  const theme = useContext(ThemeContext);
  const className = 'button-' + theme;
  return (
    <button className={className}>
      {children}
    </button>
  );
}


const root = createRoot(document.getElementById('root'));
root.render(
  <StrictMode>
    <App />
  </StrictMode>
);
</script>
<style>
* {
  box-sizing: border-box;
}

body {
  font-family: sans-serif;
  margin: 20px;
  padding: 0;
}

h1 {
  margin-top: 0;
  font-size: 22px;
}

h2 {
  margin-top: 0;
  font-size: 20px;
}

h3 {
  margin-top: 0;
  font-size: 18px;
}

h4 {
  margin-top: 0;
  font-size: 16px;
}

h5 {
  margin-top: 0;
  font-size: 14px;
}

h6 {
  margin-top: 0;
  font-size: 12px;
}

code {
  font-size: 1.2em;
}

ul {
  padding-inline-start: 20px;
}

footer {
  margin-top: 20px;
  border-top: 1px solid #aaa;
}

.panel-light,
.panel-dark {
  border: 1px solid black;
  border-radius: 4px;
  padding: 20px;
}
.panel-light {
  color: #222;
  background: #fff;
}

.panel-dark {
  color: #fff;
  background: rgb(23, 32, 42);
}

.button-light,
.button-dark {
  border: 1px solid #777;
  padding: 5px;
  margin-right: 10px;
  margin-top: 10px;
}

.button-dark {
  background: #222;
  color: #fff;
}

.button-light {
  background: #fff;
  color: #222;
}

</style>
</html>