reactjs - 类型错误 : Cannot read property 'map' of undefined"React

Question

我是 React 新手，我正在关注 React 类(class)。下面的代码出现了类似“TypeError: Cannot read property 'map' of undefined”的问题；谁能告诉发生了什么事吗？非常感谢!

import React, { Component } from 'react'

const ListGroup = props => {
    const {items,textProperty,valueProperty} = props;
    return ( 
      <ul className="list-group">
          {items.map(item =>(
         <li key={item[valueProperty]} className="list-group-item">
             {item[textProperty]}
         </li>
          ))}
          
      </ul>
     );
}
 
export default ListGroup;

Answer 1

您似乎没有将 items 属性传递给 ListGroup:

<ListGroup items=[] />

或者，您可以为项目分配默认值:

const {items = [],textProperty,valueProperty} = props;

或者使用 elvis 运算符:

items?.map(item => {})