Question

我是React.js的新手，并开始向tutorial page学习。

MacOSX Sierra v10.12

在终端，我做了：

npm install -g create-react-app
create-react-app hello-world
cd hello-world
npm start

然后，我将App.js修改为：

import React from 'react';
import ReactDOM from 'react-dom';

ReactDOM.render(
  <h1>Hello, world!</h1>,
  document.getElementById('root')
);

保存App.js后，页面上没有任何内容显示。 Screenshot

的index.html

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="shortcut icon" href="/favicon.ico">
    <!--
      Notice the use of  in the tag above.
      It will be replaced with the URL of the `public` folder during the build.
      Only files inside the `public` folder can be referenced from the HTML.

      Unlike "/favicon.ico" or "favicon.ico", "/favicon.ico" will
      work correctly both with client-side routing and a non-root public URL.
      Learn how to configure a non-root public URL by running `npm run build`.
    -->
    <title>React App</title>
  </head>
  <body>
    <div id="root"></div>
    <!--
      This HTML file is a template.
      If you open it directly in the browser, you will see an empty page.

      You can add webfonts, meta tags, or analytics to this file.
      The build step will place the bundled scripts into the <body> tag.

      To begin the development, run `npm start`.
      To create a production bundle, use `npm run build`.
    -->
  <script type="text/javascript" src="/static/js/bundle.js"></script></body>
</html>

不确定出了什么问题。请帮忙。谢谢！

Answer 1

这是你出错的地方：App.js应该是一个React组件，index.js是实际处理渲染到dom的文件。这是原始的index.js

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

ReactDOM.render(
  <App />,
  document.getElementById('root')
);

它将App作为组件导入并尝试渲染它。您基本上在App.js中创建了index.js的副本，这会破坏所有内容，因为index.js实际上是处理初始DOM呈现的。

你有两个选择：

将App.js更改为：

import React, { Component } from 'react';
import logo from './logo.svg';
import './App.css';

class App extends Component {
  render() {
    return <h1>Hello, world!</h1>
  }
}

export default App;

或在index.js中复制并粘贴您之前编写的代码。

在reactjs安装指南中的Hello-world无法正常工作

1 个答案: