React.js中的Hello-World安装指南不起作用

Question

I am completely new to React.js, and started to learn from the tutorial page . 我对React.js完全陌生，并开始从教程页面学习。

MacOSX Sierra v10.12 MacOSX Sierra v10.12

In the terminal, I did: 在终端中，我做了：

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

Then, I modified App.js to be: 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')
);

After saving App.js, nothing shows up on the page. 保存App.js后，页面上没有任何显示。 屏幕截图

index.html 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>

Not sure what went wrong. 不知道出了什么问题。 Please help. 请帮忙。 Thanks! 谢谢！

Answer 1

Here is where you went wrong: App.js is expected to be a React component, index.js is the file that actually handles rendering to the dom. 这是您出错的地方：App.js应该是React组件，index.js是实际处理渲染到dom的文件。 Here is the original index.js 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')
);

it is importing App as a component and attempting to render it. 它正在将App导入为组件并尝试呈现它。 You basically made a copy of index.js in App.js which breaks everything since index.js is what actually handles the initial DOM rendering. 您基本上在App.js中制作了index.js的副本，因为index.js是实际处理初始DOM呈现的对象，所以它破坏了所有内容。

ou have two options: 您有两种选择：

change App.js to this: 将App.js更改为此：

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;

or in the index.js copy and paste the code you wrote previously. 或在index.js中复制并粘贴您先前编写的代码。

React.js中的Hello-World安装指南不起作用

问题描述

1 个解决方案

解决方案1
1 已采纳 2016-10-27 16:47:08

React.js中的Hello-World安装指南不起作用

问题描述

1 个解决方案

解决方案1 1 已采纳 2016-10-27 16:47:08

解决方案1
1 已采纳 2016-10-27 16:47:08