REACT TO-DOリスト　作り方　簡単　

srcフォルダ内にtodo.jsを作成。
あとは写すと完成。

src/todo.js

import React, { Component } from 'react';

export default class Todo extends Component {

  constructor(props) {
    super(props);
    this.state = {
      todos: [],
      name: ''
    };
  }

  onInput = (e) => {
    this.setState({
      name: e.target.value
    });
  }
  
  addTodo = () => {
    const { todos, name } = this.state;
    this.setState({
      todos: [...todos, name]
    });
  }

  removeTodo = (index) => {
    const { todos, name } = this.state;
    this.setState({
      todos: [...todos.slice(0, index), ...todos.slice(index + 1)]
    });
  }

  render() {
    const { todos } = this.state;
    return (<div>
      <input type="text" onInput={this.onInput} />
      <button onClick={this.addTodo} >登録</button>
      <ul>
        {todos.map((todo, index) => <li key={index}>
          {todo}
          <button onClick={() => { this.removeTodo(index) }}>削除</button>
        </li>)}
      </ul>
    </div>);
  }
}

src/index.js

import React from 'react';
import ReactDOM from 'react-dom/client';
import './index.css';
// import App from './App';
import App from './todo';
import reportWebVitals from './reportWebVitals';

const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(
  <React.StrictMode>
    <App />
  </React.StrictMode>
);

// If you want to start measuring performance in your app, pass a function
// to log results (for example: reportWebVitals(console.log))
// or send to an analytics endpoint. Learn more: https://bit.ly/CRA-vitals
reportWebVitals();

結果