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

我正在开发的应用程序将react组件的名称作为小部件配置存储在浏览器存储中。其中一些组件被删除了,应用程序仍在试图呈现它们。通过清除浏览器缓存,我能够解决我的问题。

其他回答

对于我来说,这发生在我试图将命名导入作为默认导入时,所以我得到了这个错误

import ProductCard from '../../../components/ProductCard' // that what caused the issue
Error: Element 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, or you might have mixed up default and named imports.

Check the render method of `TopVente`.

所以我必须通过名称导入来修复它

import { ProductCard } from '../../../components/ProductCard'
// @flow

import React from 'react';
import { styleLocal } from './styles';
import {
  View,
  Text,
  TextInput,
  Image,
} from 'react-native';
import { TouchableOpacity } from 'react-native-gesture-handler';

export default React.forwardRef((props, ref) => {
const { onSeachClick, onChangeTextSearch , ...otherProps } = props;

  return (
        <View style={styleLocal.sectionStyle}>
        <TouchableOpacity onPress={onSeachClick}>
            <Image                              
                    source={require('../../assets/imgs/search.png')}
                    style={styleLocal.imageStyle} />
                </TouchableOpacity>
            <TextInput
                style={{ flex: 1, fontSize: 18 }}
                placeholder="Search Here"
                underlineColorAndroid="transparent"
                onChangeText={(text) => { onChangeTextSearch(text) }}
            />
        </View>
  );
});
 import IGPSSearch from '../../components/IGPSSearch';
<Search onSeachClick={onSeachClick} onChangeTextSearch= {onChangeTextSearch}> </Search>

您需要了解命名导出和默认导出。我什么时候应该用大括号导入ES6 ?

在我的例子中,我通过改变

import Provider from 'react-redux'

to

import { Provider } from 'react-redux'

当我将nothingundefined作为值传递给我创建的子组件时,发生了这个问题。我做了这个<MyComponent src="" />导致错误。然后将其更改为<MyComponent src=" " />,因为我真的不想传递任何东西…问题解决了。

就我而言,VS Code让我失望了。

这是我的组件的层次结构:

<HomeScreen> =>  <ProductItemComponent> =>  <BadgeProductComponent>

我错误地导入了ProductItemComponent。事实上,这个组件以前在共享文件夹中,但后来它被移动到主文件夹中。但是当我将文件移动到另一个文件夹时,导入没有更新,保持不变:

../shared/components

同时,组件工作正常,VS Code没有突出显示错误。但是当我添加了一个新的BadgeProductComponent到ProductItemComponent,我有一个渲染错误,并认为问题是在新的BadgeProductComponent,因为当这个组件被删除,一切工作!

更重要的是,如果我通过热键到ProductItemComponent它有。/shared/components地址,然后VS Code重定向到Home文件夹的地址../ Home /components。

通常,检查所有组件级别上所有导入的正确性。