CodeSandboxでReactに触れてみるimport React from "react" import ReactDOM from "react-dom" import "./style.css" import App from "./App" ReactDOM.render(<App />, document.getElementById("root")) import React from "react" class App extends React.Component { constructor(props) { super(props) this.state = { currentTxt: 0, num1: 0, num2: 0 } } sumNum() { this.setState({ currentTxt: parseInt(this.state.num1, 10) + parseInt(this.state.
