我在 React 中编写了一个待办事项应用程序。我为多个部分创建组件。现在，每次我尝试运行该应用程序时，它都不会显示。

我总是收到错误 Uncaught TypeError: todo is undefined in footer.js:15。

我创建了一个待办事项列表应用程序，并将所有待办事项放入一个数组中，其中有使用状态待办事项。这是我在文件页脚中的组件 Todocounter 中传递的属性。

我尝试重命名该道具并更改其在页脚中的位置，以便在正确的位置调用。

这是app.js：

import React, { useState } from 'react';
import './App.css';
import InputTodos from './input.js';
import ListTodos from './list.js';
import TodoCounter from './footer.js';
import ClearButton from './clearbutton.js';

function App() {
  // create usestates for todos
  const [todo, setTodo] = useState([]);

  // render all components i have in diffrent files
  return (
    <div className="App">
      <div className="container">
        <div className="header">
          <InputTodos todo={todo} setTodo={setTodo} />
        </div>
        <div className="containerMid">
          <ListTodos todo={todo} />
        </div>
        <div className="footer">
          <TodoCounter todo={todo} />
        </div>
        <div className="buttonCleardiv">
          <ClearButton todo={todo} setTodo={setTodo} />
        </div>
      </div>
    </div>
  );
}

export default App;

这是 footer.js：

import React, { useEffect, useState } from 'react';

import './App.css';

// use effect to show whenever the array will change from completed todos to not completed
function TodoCounter(props) {
  const { todo } = props;
  const [completed, setCompleted] = useState(0);
  const [notCompleted, setNotCompleted] = useState(0);

  // filter between completed todos and not completed todos with cheackking the bolean status
  function counttodos(props) {
    const { todo } = props;
    return {
      completed: todo.filter((todo) => todo.isChecked).length,
      notCompleted: todo.filter((todo) => !todo.isChecked).length,
    };
  }
  //with the useeffect hook set the todos on completed or not completed if sth changes on the todos
  useEffect(() => {
    const { completed, notcompleted } = counttodos(todo);
    setCompleted(completed);
    setNotCompleted(notcompleted);
  }, [todo]);

  return (
    <div>
      <p>Completed: {completed}</p>
      <p>Not Completed: {notCompleted}</p>
      <p>Todos: {todo.length} </p>
    </div>
  );
}

export default TodoCounter;