Question

如何从事件处理程序中的对象中打印多个键？

这是我的代码的链接-https://codesandbox.io/s/suspicious-hamilton-erkqv

在行35上的

我用对象“ x”调用事件处理程序ChangeName。我能够打印一个称为“名称”（x.name）的键我该如何打印x对象的所有3个道具（名称，id，类型）？

试图将x转换为带有object.keys（x）的数组，但是当我循环遍历输出时，出现错误，提示无法使用map函数

 const ChangeName = x => {
    setvalue(x.name);
  };


  <div>{value}</div> // display the results

Answer 1

您的值不是数组，它是一个对象，这就是为什么您不能使用map方法的原因，这就是它的工作原理：

import React, { useState, useEffect } from "react";
import ReactDOM from "react-dom";

function App() {
  const [posts, setposts] = useState([]);
  const [value, setvalue] = useState("");

  useEffect(() => {
    const posts = [
      {
        id: 1,
        name: "Name 1",
        type: "Type 1"
      },
      {
        id: 2,
        name: "Name 2",
        type: "Type 2"
      },
      {
        id: 3,
        name: "Name 3",
        type: "Type 3"
      },
      {
        id: 4,
        name: "Name 4",
        type: "Type 4"
      }
    ];

    setposts(posts);
  }, []);

  const ChangeName = x => {
    setvalue(x);
  };

  return (
    <div>
      <ul>
        {posts.map(post => (
          <li key={post.id}>
            {post.name},{post.type}
            <button onClick={() => ChangeName(post)}>More Info</button>
          </li>
        ))}
      </ul>

      <div>
        {value.name}
        {value.id}
        {value.type}
      </div>
    </div>
  );
}

const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);

Answer 2

运行代码：


import React, { useState, useEffect } from "react";
import ReactDOM from "react-dom";

function App() {
  const [posts, setposts] = useState([]);
  const [values, setvalue] = useState([]);

  useEffect(() => {
    const posts = [
      {
        id: 1,
        name: "Name 1",
        type: "Type 1"
      },
      {
        id: 2,
        name: "Name 2",
        type: "Type 2"
      },
      {
        id: 3,
        name: "Name 3",
        type: "Type 3"
      },
      {
        id: 4,
        name: "Name 4",
        type: "Type 4"
      }
    ];

    setposts(posts);
  }, []);

  const ChangeName = x => {
    console.log(Object.values(x));
    Object.values(x).map(k => setvalue(k));
  };

  return (
    <div>
      <ul>
        {posts.map(post => (
          <li key={post.id}>
            {post.name},{post.type}
            <button onClick={ChangeName.bind(this, post)}>More Info</button>
          </li>
        ))}
      </ul>

      <div>{values}</div>
    </div>
  );
}

const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);

您需要将值设置为非值。

我如何从一个对象中提取多个键并打印输出

2 个答案: