您好，我是新的编码，并开始学习React，我有一个问题，当我改变在h1标签的网页只更新在私人浏览器的html。是否有任何原因导致这一点或我所犯的任何错误。提前谢谢。

import React, { Component } from "react";
import { render } from "react-dom";
export default class App extends Component {
  constructor(props) {
    super(props);
  }
  render() {
    return <h1>Why does this </h1>;
  }
}
const appDiv = document.getElementById("app");
render(<App />, appDiv);