Javascript 在REACT中渲染有困难

我无法渲染名为Butcher Shop的组件。为了使它不为null或未定义，我无法找出我缺少了什么。有人能发现错误吗？没有任何内容正在打印到DOM。这是我得到的错误：TypeError:Super表达式必须为null或函数，而不是未定义的

40 |出口级屠宰厂扩展反应组件{

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你有一个简单的书写错误，应该是

导出类ButcherShop扩展React.Component{

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请注意大写的C

我看到了几个问题，您还需要将类转换为类名。如果我在InforontofYou的return中添加了一些文本，它会呈现出来。请查看您的“return”以查看它是否正确

主要问题：组件应该大写： 另外，考虑下面的语法

    export class ButcherShop extends React.Component{
      render() {
      return 
      <div class="butcher-shop">
       <div>
        <p>'Hello! We have the following products for sale today'</p>
        <ul>
          <li>'Tenderloin'</li>
          <li>'Short ribs'</li>
          <li>'Beef shin'</li>
          <li>'Ribeye'</li>
        </ul>
       </div>
      </div>
      }
    }

---

这是因为您没有返回在渲染方法中创建的元素

将所有React.createElement元素保存到一个变量中，并在返回时使用该变量：

export class ButcherShop extends React.Component{
    render() {
        const content = React.createElement('div', {},
                React.createElement('p', {}, 'Hello! We have the following products for sale today'),
                React.createElement('ul', {},
                [
                    React.createElement('li', {}, 'Tenderloin'),
                    React.createElement('li', {}, 'Short ribs'),
                    React.createElement('li', {}, 'Beef shin'),
                    React.createElement('li', {}, 'Ribeye')
                ]));
        return <div class="butcher-shop">{content}</div>
    }
}

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组件呈现方法的工作方式与此相同。您需要实际返回您创建的元素。

我建议您最好使用JSX。 我为您留下一个链接，供您学习如何使用： . 以下是使用JSX时代码的外观示例：

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

const BUTCHER_PRODUCTS = [
'Tenderloin',
'Short ribs',
'Beef shin',
'Ribeye'
];

export class OlderCoaster extends React.Component {
render(){
 return(
    <div className="oldercoaster">
        <p>Two grannies having the time of their life!</p>
        <p>Passengers:</p>
        <ul>
            <li>Anges</li>
            <li>miruel</li>
        </ul>
    </div>
 )}};

 export class InFrontOfYou extends React.Component{
 render() {
  return(
    <div>
        <p>You shouldnt look too far</p>
        <p>Sometimes, the soultion is right in from of you</p>
    </div>
    )
  );
  };

  export class ButcherShop extends React.Component{
   render() {
    return(
      <div className="butcher-shop">
      <p>Hello! We have the following products for sale today</p>
      <ul>
          <li>Tenderloin</li>
          <li>Short ribs</li>
          <li>Beef shin</li>
          <li>Ribeye</li>
      </ul>
     </div>
   )
 }

   ReactDOM.render(
  <div>
      <OlderCoaster/>
      <InFrontOfYou/>
      <ButcherShop/>
  </div>,
document.getElementById('global')
);

---

这不应该是第40行的React.Component而不是React.Component吗？太棒了。谢谢！为什么不使用JSX来代替调用JS代码。它易于阅读和维护。这样就消除了错误，但是页面仍然是空白的。我感觉这与顶部的butcher_products数组有关。@davidhazlettjr这是因为你不是返回在渲染方法中创建的元素。将所有React.createElement元素保存到一个变量中，并在返回中使用该变量：return{elements}

ReactDOM.render(
    React.createElement('div', {}, [
      React.createElement(OlderCoaster),
      React.createElement(InFrontOfYou),
      React.createElement(ButcherShop)
    ]),
    document.getElementById('global')
  );

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

const BUTCHER_PRODUCTS = [
'Tenderloin',
'Short ribs',
'Beef shin',
'Ribeye'
];

export class OlderCoaster extends React.Component {
render(){
 return(
    <div className="oldercoaster">
        <p>Two grannies having the time of their life!</p>
        <p>Passengers:</p>
        <ul>
            <li>Anges</li>
            <li>miruel</li>
        </ul>
    </div>
 )}};

 export class InFrontOfYou extends React.Component{
 render() {
  return(
    <div>
        <p>You shouldnt look too far</p>
        <p>Sometimes, the soultion is right in from of you</p>
    </div>
    )
  );
  };

  export class ButcherShop extends React.Component{
   render() {
    return(
      <div className="butcher-shop">
      <p>Hello! We have the following products for sale today</p>
      <ul>
          <li>Tenderloin</li>
          <li>Short ribs</li>
          <li>Beef shin</li>
          <li>Ribeye</li>
      </ul>
     </div>
   )
 }

   ReactDOM.render(
  <div>
      <OlderCoaster/>
      <InFrontOfYou/>
      <ButcherShop/>
  </div>,
document.getElementById('global')
);