如何將class添加到ReactJS中點擊的項目

Question

我有一個對象數組，其中包含導航欄鏈接的鍵對值，我已將數組映射到列表並成功呈現它，但是當我嘗試將 class 添加到僅活動鏈接時，它會將 class 添加到所有鏈接項。

想知道我哪里出錯了嗎？

import React, { Component } from "react";
import { Link } from "react-router-dom";

class SideNavbar extends Component {
  constructor(props) {
    super(props);
    this.state = [
      { id: 1, name: "Link1", to: "/cms", className: "side_nav_item" },
      { id: 2, name: "Link2", to: "/cms", className: "side_nav_item" },
      { id: 3, name: "Link3", to: "/cms", className: "side_nav_item" },
      { id: 4, name: "Link4", to: "/cms", className: "side_nav_item" }
    ];
  }

  handleClick = () => {
    const currentClass = document.getElementsByClassName("side_nav_item");
    for (let i = 0; i < currentClass.length; i++) {
      currentClass[i].classList.toggle("active_item");
      console.log(currentClass[i]);
    }
  };
  render() {
    const navLinks = this.state.map(link => {
      return (
        <div key={link.id}>
          <ul>
            <li onClick={this.handleClick} className={link.className}>
              <Link to={link.to}>{link.name}</Link>
            </li>
          </ul>
        </div>
      );
    });
    return <div>{navLinks}</div>;
  }
}

export default SideNavbar;

Answer 1

與其嘗試手動操作 DOM，您還可以保留一段稱為例如activeLink的狀態，該狀態存儲活動鏈接的 id，您可以使用該 ID 將類應用於渲染方法中的活動鏈接。

例子

 class SideNavbar extends React.Component { state = { links: [ { id: 1, name: "Link1", to: "/cms", className: "side_nav_item" }, { id: 2, name: "Link2", to: "/cms", className: "side_nav_item" }, { id: 3, name: "Link3", to: "/cms", className: "side_nav_item" }, { id: 4, name: "Link4", to: "/cms", className: "side_nav_item" } ], activeLink: null }; handleClick = id => { this.setState({ activeLink: id }); }; render() { const { links, activeLink } = this.state; return ( <div> {links.map(link => { return ( <div key={link.id}> <ul> <li onClick={() => this.handleClick(link.id)} className={ link.className + (link.id === activeLink ? " active_item" : "") } > {link.name} {link.id === activeLink && "active!"} </li> </ul> </div> ); })} </div> ); } } ReactDOM.render(<SideNavbar />, document.getElementById("root"));

 <script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script> <div id="root"></div>

Answer 2

問題是這行代碼：
const currentClass = document.getElementsByClassName('side_nav_item');

正在使用side_nav_items CSS 類抓取所有HTML元素，在您的情況下，這就是您的所有側面導航鏈接。 您可能想要使用：

let element = document.getElementById(id);

只需獲取由其id標識的點擊側導航元素。 然后你可以使用element.classList.add('active_item'); 將active_item css 類添加到選定的側邊導航項。

希望這有幫助！

Answer 3

一段時間前我一直在努力解決這個問題，這個解決方案對我有用

const pathName = useLocation().pathname;

然后在您的 Link 元素中，您可以簡單地執行className={pathName === link.to? 'active_item': ''} className={pathName === link.to? 'active_item': ''}