尝试得到react-router (v4.0.0)和react-hot loader (3.0.0-beta.6)很好地发挥,但在浏览器控制台得到以下错误:

Warning: React.createElement: type is invalid -- expected a string
(for built-in components) or a class/function (for composite
components) but got: undefined. You likely forgot to export your
component from the file it's defined in.

index.js:

import React from 'react';
import ReactDom from 'react-dom';
import routes from './routes.js';
require('jquery');
import 'bootstrap/dist/css/bootstrap.min.css';
import 'bootstrap/dist/js/bootstrap.min.js';
import './css/main.css';

const renderApp = (appRoutes) => {
    ReactDom.render(appRoutes, document.getElementById('root'));
};

renderApp( routes() );

routes.js:

import React from 'react';
import { AppContainer } from 'react-hot-loader';
import { Router, Route, browserHistory, IndexRoute } from 'react-router';
import store from './store/store.js';
import { Provider } from 'react-redux';
import App from './containers/App.jsx';
import Products from './containers/shop/Products.jsx';
import Basket from './containers/shop/Basket.jsx';

const routes = () => (

    <AppContainer>
        <Provider store={store}>
            <Router history={browserHistory}>
                <Route path="/" component={App}>
                    <IndexRoute component={Products} />
                    <Route path="/basket" component={Basket} />
                </Route>
            </Router>
        </Provider>
    </AppContainer>

);

export default routes;

当前回答

我认为在排除这个错误时最重要的一点是,当您试图实例化一个不存在的组件时,它就会显现出来。这个组件不需要导入。在我的例子中,我将组件作为属性传递。我忘记更新其中一个调用,以便在一些重构之后正确地传递组件。不幸的是,由于JS不是静态类型的,我的错误没有被发现,它花了一些时间来弄清楚发生了什么。

要排除此错误,在呈现组件之前检查该组件,以确保它是您所期望的组件类型。

其他回答

大多数情况下,这表示导入/导出错误。但是要注意,不仅要确保堆栈跟踪中引用的文件本身得到了良好的导出,还要确保该文件正确地导入了其他组件。在我的例子中,错误是这样的:

import React from //注意末尾的.css,这是错误的原因! import SeeminglyUnimportantComponent from './SeeminglyUnimportantComponent.css'; Const组件= (props) => ( < div > < SeeminglyUnimportantComponent / > {/ *……这里的组件代码*/} < / div > ); 导出默认组件;

在我的例子中,我添加了相同的自定义组件作为道具,而不是实际的道具

   import AddAddress from '../../components/Manager/AddAddress';
    
    class Add extends React.PureComponent {
      render() {
        const {
          history,
          addressFormData,
          formErrors,
          addressChange,
          addAddress,
          isDefault,
          defaultChange
        } = this.props;
    

错误:

    return (
        <AddAddress
          addressFormData={addressFormData}
          formErrors={formErrors}
          addressChange={addressChange}
          addAddress={AddAddress} // here i have used the Component name as probs in same component itself instead of prob
          isDefault={isDefault}
          defaultChange={defaultChange}
        />
      </SubPage>

解决方案:

return (
    <AddAddress
      addressFormData={addressFormData}
      formErrors={formErrors}
      addressChange={addressChange}
      addAddress={addAddress} // removed the component name and give prob name
      isDefault={isDefault}
      defaultChange={defaultChange}
    />
  </SubPage>

试试这个

npm i react-router-dom@next

在你的App.js中

import { BrowserRouter as Router, Route } from 'react-router-dom'

const Home = () => <h1>Home</h1>

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

export default App;

循环依赖也是原因之一。(一般)

对我来说,删除Switch解决了这个问题

import React from "react";
import "./styles.css";
import { Route, BrowserRouter, Routes } from "react-router-dom";
import LoginPage from "./pages/LoginPage";
import HomePage from "./pages/HomePage";

export default function App() {
  return (
    <BrowserRouter>
      <Routes>
        <Route exact path="/" element={<HomePage />} />
        <Route path="/login" element={<LoginPage />} />
      </Routes>
    </BrowserRouter>
  );
}