javascript - React 报错'Warning : React. createElement : type should not be null, undefined 如何解决？

Question

我是 reactjs 的新手，正在尝试按照 Fullstack.io 中的教程实现 reactjs 应用程序.当我读到本教程的一半时，我在运行 npm run test 时收到错误。

app.js:

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

import 'font-awesome/css/font-awesome.css'


import App from 'containers/App/App'

import './app.css'

import {browserHistory, Router, Route} from 'react-router'

const Home = React.createClass({
  render: function() {
    return (<div>Hello world</div>)
  }
})

const routes = (
  <Router>
    <Route path="/" component={Home} />
  </Router>
)



const mountNode = document.querySelector('#root');
ReactDOM.render(
  <App history={browserHistory} />, mountNode);

App.js

import React, { PropTypes } from 'react'; 
import ReactDOM from 'react-dom' 
import { Router } from 'react-router'; 
class App extends React.Component { 
   static propTypes = { 
      routes: PropTypes.object.isRequired, 
      history: PropTypes.object.isRequired 
   }
   get content() { 
       return (
            <Router routes={this.props.routes} history={this.props.history} />
        ) 
    } 
    render() { 
       return ( 
          <div style={ { height: '100%' } }> {this.content} </div>
        ) 
    }
  } 
export default App;

我找不到错误在哪里，谁能帮我解决这个问题？

报错截图如下:

Answer 1

您没有导出您的 App 组件。

改成

import React, { PropTypes } from 'react'; 
import ReactDOM from 'react-dom' 
import { Router } from 'react-router'; 
export default class App extends React.Component { 
   static propTypes = { 
      routes: PropTypes.object.isRequired, 
      history: PropTypes.object.isRequired 
   }
   get content() { 
       return (
            <Router routes={this.props.routes} history={this.props.history} />
        ) 
    } 
    render() { 
       return ( 
          <div style={ { height: '100%' } }> {this.content} </div>
        ) 
    }
  } 

注意 export 关键字。