tekknolagi/app.tsx

## app.tsx
import React, { useCallback, useEffect, useReducer } from "https://esm.sh/react@18.2.0"

const STATE_KEY = "mystate";
const INITIAL_STATE = { age: 42, name: null };

function loadState() {
  return JSON.parse(localStorage.getItem(STATE_KEY)) || INITIAL_STATE;
}

function reducer(state, action) {
  if (action.type === 'inc_age') {
    return {
      ...state,
      age: state.age + 1
    };
  } else if (action.type === 'set_name') {
    return {
      ...state,
      name: action.name,
    };
  } else if (action.type === 'clear') {
    return INITIAL_STATE;
  }
  throw Error('Unknown action.');
}

const App = () => {
  const [state, dispatch] = useReducer(reducer, null, loadState);
  useEffect(() => {
    localStorage.setItem(STATE_KEY, JSON.stringify(state));
  }, [state]);
  const handleNameChange = e => dispatch({type: 'set_name', name: e.target.value });
  const handleAgeIncrement = e => dispatch({type: 'inc_age' });
  const handleClearStorage = e => dispatch({type: 'clear'});
  const formName = state.name === null ? "" : state.name;
  const renderedName = (state.name === null || state.name === "") ? "unknown user" : state.name;
  return (
    <>
      <input onChange={handleNameChange} value={formName} />
      <button onClick={handleAgeIncrement}>Increment age</button>
      <p>Hello {renderedName}! You are {state.age}.</p>
      <button onClick={handleClearStorage}>Clear localStorage</button>
    </>
  );
};

export default App

## index.html
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>React App</title>
    <link rel="stylesheet" href="./style.css">
  </head>
  <body>
    <div id="root"></div>
    <script type="module" src="./main.tsx"></script>
  </body>
</html>

## main.tsx
import React from "https://esm.sh/react@18.2.0"
import { createRoot } from "https://esm.sh/react-dom@18.2.0/client"
import App from "./app.tsx"

const root = createRoot(document.getElementById("root"))
root.render(<App />)

## style.css
* {
  padding: 0;
  margin: 0;
  line-height: 1.5;
}

div {
  width: 100vw;
  height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
}

h1 {
  font-size: 32px;
  font-family: Inter, sans-serif;
}

p {
  font-size: 16px;
  font-style: italic;
}

button {
  font-size: 30px;
}
	import React, { useCallback, useEffect, useReducer } from "https://esm.sh/react@18.2.0"

	const STATE_KEY = "mystate";
	const INITIAL_STATE = { age: 42, name: null };

	function loadState() {
	return JSON.parse(localStorage.getItem(STATE_KEY)) \|\| INITIAL_STATE;
	}

	function reducer(state, action) {
	if (action.type === 'inc_age') {
	return {
	...state,
	age: state.age + 1
	};
	} else if (action.type === 'set_name') {
	return {
	...state,
	name: action.name,
	};
	} else if (action.type === 'clear') {
	return INITIAL_STATE;
	}
	throw Error('Unknown action.');
	}

	const App = () => {
	const [state, dispatch] = useReducer(reducer, null, loadState);
	useEffect(() => {
	localStorage.setItem(STATE_KEY, JSON.stringify(state));
	}, [state]);
	const handleNameChange = e => dispatch({type: 'set_name', name: e.target.value });
	const handleAgeIncrement = e => dispatch({type: 'inc_age' });
	const handleClearStorage = e => dispatch({type: 'clear'});
	const formName = state.name === null ? "" : state.name;
	const renderedName = (state.name === null \|\| state.name === "") ? "unknown user" : state.name;
	return (
	<>
	<input onChange={handleNameChange} value={formName} />
	<button onClick={handleAgeIncrement}>Increment age</button>
	<p>Hello {renderedName}! You are {state.age}.</p>
	<button onClick={handleClearStorage}>Clear localStorage</button>
	</>
	);
	};

	export default App
	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="utf-8">
	<title>React App</title>
	<link rel="stylesheet" href="./style.css">
	</head>
	<body>
	<div id="root"></div>
	<script type="module" src="./main.tsx"></script>
	</body>
	</html>
	import React from "https://esm.sh/react@18.2.0"
	import { createRoot } from "https://esm.sh/react-dom@18.2.0/client"
	import App from "./app.tsx"

	const root = createRoot(document.getElementById("root"))
	root.render(<App />)
	* {
	padding: 0;
	margin: 0;
	line-height: 1.5;
	}

	div {
	width: 100vw;
	height: 100vh;
	display: flex;
	flex-direction: column;
	align-items: center;
	justify-content: center;
	text-align: center;
	}

	h1 {
	font-size: 32px;
	font-family: Inter, sans-serif;
	}

	p {
	font-size: 16px;
	font-style: italic;
	}

	button {
	font-size: 30px;
	}