反应。类型无效——期望为字符串

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

反应。片段

为我修正了这个问题

错误代码:

 return (
            <section className={classes.itemForm}>
             <Card>
             </Card> 
            </section>
      );

Fix

 return (
      <React.Fragment>
        <section className={classes.itemForm}>
         <Card>
         </Card> 
        </section>
      </React.Fragment>
  );

2020-05-08 06:29:55

其他回答

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>
  );
}

2022-01-18 10:53:01

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。

2022-03-18 15:50:56

我所缺少的是我正在使用

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

正确答案应该是:

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

当然你需要添加npm包react-router-dom:

npm install react-router-dom@next --save

2017-08-01 11:21:35

简而言之，不知何故发生了以下情况:

render() {
    return (
        <MyComponent /> // MyComponent is undefined.
    );
}

它不一定与某些不正确的输入或输出有关:

render() {
    // MyComponent may be undefined here, for example.
    const MyComponent = this.wizards[this.currentStep];

    return (
        <MyComponent />
    );
}

2018-12-18 16:53:46

我刚刚花了30分钟来解决这个基本的问题。

我的问题是我导入react原生元素

例如导入React，{文本，图像，组件}从' React ';

并试图使用它们，这导致我收到这个错误。

一旦我从<文本>切换到<p>和<图像>到<img>，一切都按预期工作。

2019-03-31 22:13:23

反应。类型无效——期望为字符串

推荐文章

最新文章

标签