如何使用React（函陣列件）洗掉串列項

只是在練習一個簡單的待辦事項串列，我希望能夠單擊串列中的一個專案將其洗掉。我想我已經非常接近了，但無法弄清楚如何從單擊的 li 中獲取某種資料以將其與我的陣列進行比較。

應用程式.js

import { useState } from "react";
import "./App.css";
import Newtodo from "./NewTodo/NewTodo";
import TodoList from "./TodoList/TodoList";

let INITIAL_TODOS = [
  { id: "e1", title: "Set up meeting", date: new Date(2021, 0, 14), index: 0 },
  {
    id: "e2",
    title: "Doctor appointment",
    date: new Date(2021, 2, 14),
    index: 1,
  },
  { id: "e3", title: "Work on project", date: new Date(2021, 1, 22), index: 2 },
  { id: "e4", title: "Update resume", date: new Date(2021, 6, 14), index: 3 },
];

const App = () => {
  const [todos, setTodos] = useState(INITIAL_TODOS);

  const deleteItem = (e) => {
    const newTodos = todos.filter((item) => item.index !== 1 /*This works properly with a hardcoded value(1) but how can this be done dynamically as e doesn't seem to have anything useful within it (like e.target.value)*/);
    setTodos(newTodos);
  };

  return (
    <div className="App">
      <Newtodo />
      <TodoList items={todos} handleDelete={deleteItem} />
    </div>
  );
};

export default App;

TodoList.js

import "./TodoList.css";
import Todo from "./Todo";

const TodoList = (props) => {
  return (
    <div className="todo-list">
      <ul>
        {props.items.map((todo, i) => (
          <Todo
            index={i}
            key={todo.id}
            title={todo.title}
            date={todo.date}
            handleDelete={props.handleDelete}
          />
        ))}
      </ul>
    </div>
  );
};

export default TodoList;

待辦事項.js

import "./Todo.css";

const Todo = (props) => {
  const month = props.date.toLocaleString("en-US", { month: "long" });
  const day = props.date.toLocaleString("en-US", { day: "2-digit" });
  const year = props.date.getFullYear();

  return (
    <li onClick={props.handleDelete} className="todo-item">
      <h2>{props.title}</h2>
      <span>
        {day}, {month}, {year}
      </span>
    </li>
  );
};

export default Todo;

任何幫助或指導將不勝感激！

uj5u.com熱心網友回復：

您需要傳遞要洗掉的元素的索引。在洗掉處理程式中按索引不等于傳遞索引的元素過濾

const deleteItem = (index) => {
  setTodos(todos => todos.filter((item, i) => i !== index));
};

并且在映射中

const TodoList = (props) => {
  return (
    <div className="todo-list">
      <ul>
        {props.items.map((todo, i) => (
          <Todo
            index={i}
            key={todo.id}
            title={todo.title}
            date={todo.date}
            handleDelete={() => props.handleDelete(i)}
          />
        ))}
      </ul>
    </div>
  );
};

改用該id屬性可能會更好。

const deleteItem = (id) => {
  setTodos(todos => todos.filter((item) => item.id !== id));
};

...

const TodoList = (props) => {
  return (
    <div className="todo-list">
      <ul>
        {props.items.map((todo, i) => (
          <Todo
            index={i}
            key={todo.id}
            title={todo.title}
            date={todo.date}
            handleDelete={() => props.handleDelete(todo.id)}
          />
        ))}
      </ul>
    </div>
  );
};

并且為了避免子組件中的匿名回呼，宣告handleDelete為柯里化函式。

const deleteItem = (id) => () => {
  setTodos(todos => todos.filter((item) => item.id !== id));
};

...

const TodoList = (props) => {
  return (
    <div className="todo-list">
      <ul>
        {props.items.map((todo, i) => (
          <Todo
            index={i}
            key={todo.id}
            title={todo.title}
            date={todo.date}
            handleDelete={props.handleDelete(todo.id)}
          />
        ))}
      </ul>
    </div>
  );
};

uj5u.com熱心網友回復：

首先，您需要將您的待辦事項 id 傳遞給 handle delete 然后您可以在那里訪問 id

{ props.items.map((todo, i) => (
          <Todo
            index={i}
            key={todo.id}
            title={todo.title}
            date={todo.date}
            handleDelete={()=> props.handleDelete(todo.id)}
          />
        ))}

您在此處訪問 ID

  const deleteItem = (todoId) => {
     const newTodos = todos.filter((item) => item.id !== todoId;
    setTodos(newTodos);
  };

uj5u.com熱心網友回復：

data-index在 Todo.js 中添加屬性

<li data-index={props.index} onClick={props.handleDelete} className="todo-item">
  <h2>{props.title}</h2>
  <span>
   {day}, {month}, {year}
  </span>
</li>

并將其洗掉 deleteTodo

const deleteItem = (e) => {
    const newTodos = todos.filter((item) =>  item.index !==  e.currentTarget.dataset.index)
    setTodos(newTodos);
  };

標籤：javascript 反应 列表 反应功能组件

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