在 react.js 中导出多个模块 [英] exporting multiple modules in react.js

问题描述

刚接触 react.js 并尝试遵循 教程.不幸的是，页面中给出的代码不起作用.webpack 抱怨了

 ./App.jsx 中的错误模块构建失败:语法错误:每个模块只允许一个默认导出.

想知道如何修复它.谢谢.

=== App.jsx====

从'react'导入React；从 'react-dom' 导入 ReactDOM；import { Router, Route, Link, browserHistory, IndexRoute } from 'react-router'类 App 扩展了 React.Component {使成为() {返回 (<div><ul><li><Link to = "/home">Home</Link></li><li><Link to = "/about">About</Link></li><li><Link to = "/contact">联系方式</Link></li>{this.props.children}

)}}导出默认应用程序；class Home 扩展 React.Component {使成为() {返回 (<div><h1>首页...</h1>

)}}导出默认首页；class 关于扩展 React.Component {使成为() {返回 (<div><h1>关于...</h1>

)}}导出默认关于；class Contact 扩展 React.Component {使成为() {返回 (<div><h1>联系...</h1>

)}}导出默认联系人；

=== main.js ===

从'react'导入React；从 'react-dom' 导入 ReactDOM；从'./App.jsx'导入应用程序；ReactDOM.render(, document.getElementById('app'));

更新1

我注释掉了所有的export default 并在最后添加了以下内容

module.exports = {应用程序:应用程序，家:家，关于:关于，联系方式:联系方式}

现在没有编译错误但是网页是空白的.我不确定这里出了什么问题.

解决方案

你只能有一个你声明的默认导出:

导出默认应用；或者export default class App extends React.Component {...

然后做 import App from './App'

如果你想导出更多的东西，你可以使用 named 导出，你声明它没有 default 关键字，例如:

export {关于，接触，}

或:

export 关于；出口联系方式；

或:

export const About = class About extends React.Component {....export const Contact = () =>(<div> ... </div>);

然后你像这样导入它们:

import App, { About, Contact } from './App';

教程中有一个错误，因为不可能在同一个 main.js 文件中进行 3 个默认导出.除此之外，如果在文件之外没有使用任何东西，为什么要导出任何东西?.正确的 main.js :

从'react'导入React；从 'react-dom' 导入 ReactDOM；import { Router, Route, Link, browserHistory, IndexRoute } from 'react-router'类 App 扩展了 React.Component {...}class Home 扩展 React.Component {...}class 关于扩展 React.Component {...}class Contact 扩展 React.Component {...}ReactDOM.render((<路由器历史记录 = {browserHistory}><路由路径=/"组件={App}><IndexRoute 组件 = {Home}/><Route path = "home" component = {Home}/><路由路径=关于"组件={关于}/><路由路径=联系方式"组件={联系方式}/></路线></路由器>), document.getElementById('app'))

另一件事是本教程基于 react-router-V3，它具有与 v4 不同的 api.

New to react.js and trying to following tutorial. Unfortunately the code given in the page didn't work. webpack complained

ERROR in ./App.jsx
Module build failed: SyntaxError: Only one default export allowed per module.

Wonder how to fix it. Thanks.

=== App.jsx====

import React from 'react';
import ReactDOM from 'react-dom';
import { Router, Route, Link, browserHistory, IndexRoute  } from 'react-router'

class App extends React.Component {
   render() {
      return (
         <div>
            <ul>
               <li><Link to = "/home">Home</Link></li>
               <li><Link to = "/about">About</Link></li>
               <li><Link to = "/contact">Contact</Link></li>
            </ul>

           {this.props.children}
         </div>
      )
   }
}

export default App;

class Home extends React.Component {
   render() {
      return (
         <div>
            <h1>Home...</h1>
         </div>
      )
   }
}

export default Home;

class About extends React.Component {
   render() {
      return (
         <div>
            <h1>About...</h1>
         </div>
      )
   }
}

export default About;

class Contact extends React.Component {
   render() {
      return (
         <div>
            <h1>Contact...</h1>
         </div>
      )
   }
}

export default Contact;

=== main.js ===

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App.jsx';

ReactDOM.render(<App/>, document.getElementById('app'));

UPDATE1

I commented out all the export default and added the following at the end

module.exports = {
    App: App,
    Home: Home,
    About: About,
    Contact: Contact
}

Now there is no compile error but the web page is a blank. I am not sure what is wrong here.

解决方案

You can have only one default export which you declare like:

export default App; or export default class App extends React.Component {...

and later do import App from './App'

If you want to export something more you can use named exports which you declare without default keyword like:

export {
  About,
  Contact,
}

or:

export About;
export Contact;

or:

export const About = class About extends React.Component {....
export const Contact = () => (<div> ... </div>);

and later you import them like:

import App, { About, Contact } from './App';

EDIT:

There is a mistake in the tutorial as it is not possible to make 3 default exports in the same main.js file. Other than that why export anything if it is no used outside the file?. Correct main.js :

import React from 'react';
import ReactDOM from 'react-dom';
import { Router, Route, Link, browserHistory, IndexRoute  } from 'react-router'

class App extends React.Component {
...
}

class Home extends React.Component {
...
}


class About extends React.Component {
...
}


class Contact extends React.Component {
...
}


ReactDOM.render((
   <Router history = {browserHistory}>
      <Route path = "/" component = {App}>
         <IndexRoute component = {Home} />
         <Route path = "home" component = {Home} />
         <Route path = "about" component = {About} />
         <Route path = "contact" component = {Contact} />
      </Route>
   </Router>

), document.getElementById('app'))

EDIT2:

another thing is that this tutorial is based on react-router-V3 which has different api than v4.

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