这里有几个问题。首先，远离直接操作DOM. React 使用 virtual DOM，因此您无需手动添加或删除DOM元素。ReactDOM通过render方法自动处理这种操作。此外，您需要Modal使用某种state（isOpen）来控制它。它可以通过 React 的本地状态或通过 Redux 的状态。无论哪种方式，都需要对其进行控制和比较。简而言之，如果它是打开的，渲染Modal，如果它关闭，渲染null。

此外，该Modal组件可以构建为可重用的。只需将它作为 a 添加child到另一个有状态parent组件，并在其中包含children您想要呈现的任何内容。

工作示例：

components/Example.js（父组件）

import React, { Component } from "react";
import Modal from "../Modal";
import "./styles.css";

class Example extends Component {
  state = { isOpen: false };

  handleOpenModal = () => {
    this.setState({ isOpen: true });
  };

  handleCloseModal = () => {
    this.setState({ isOpen: false });
  };

  render = () => (
    <div className="example">
      <h2>Simple Modal Example</h2>
      <button
        className="uk-button uk-button-primary uk-button-small"
        onClick={this.handleOpenModal}
      >
        Open Modal
      </button>
      <Modal isOpen={this.state.isOpen} onCloseModal={this.handleCloseModal}>
        <h1 className="title">Hello!</h1>
        <p className="subtitle">There are two ways to close this modal</p>
        <ul>
          <li>Click outside of this modal in the grey overlay area.</li>
          <li>Click the close button below.</li>
        </ul>
        <button
          className="uk-button uk-button-danger uk-button-small"
          onClick={this.handleCloseModal}
        >
          Close
        </button>
      </Modal>
    </div>
  );
}

export default Example;

components/Modal.js（子组件——它有很多较小的组件，为了可重用性和易于理解而分开——它们基本上是简单div的，styles附加了一些——见下面的注释）

import React from "react";
import PropTypes from "prop-types";
import BackgroundOverlay from "../BackgroundOverlay"; // grey background
import ClickHandler from "../ClickHandler"; // handles clicks outside of the modal
import Container from "../Container"; // contains the modal and background
import Content from "../Content"; // renders the "children" placed inside of <Modal>...</Modal>
import ModalContainer from "../ModalContainer"; // places the modal in the center of the page

// this is a ternary operator (shorthand for "if/else" -- if cond ? then : else)
// below can be read like: if isOpen is true, then return/render the modal, else return null
const Modal = ({ children, isOpen, onCloseModal }) =>
  isOpen ? (
    <Container>
      <BackgroundOverlay />
      <ModalContainer>
        <ClickHandler isOpen={isOpen} closeModal={onCloseModal}>
          <Content>{children}</Content>
        </ClickHandler>
      </ModalContainer>
    </Container>
  ) : null;

// these proptype declarations are to ensure that passed down props are 
// consistent and are defined as expected
Modal.propTypes = {
  children: PropTypes.node.isRequired, // children must be a React node
  isOpen: PropTypes.bool.isRequired, // isOpen must be a boolean
  onCloseModal: PropTypes.func.isRequired // onCloseModal must be a function
};

export default Modal;

看起来您的模态是打开的，这仅取决于它是否由父级呈现。除了重新构建此模式之外，实现您想要的唯一方法是传入某种 onClose 回调：

class Parent extends React.Component {
  state = { isModalOpen: false };

  render() {
    return (<div>
      // Stuff
      {this.state.isModalOpen &&
        <Modal onClose={() => this.setState({ isModalOpen: false })}/>
      }
      // Stuff
    </div>);
  }
}

在您的Modal：

<div className="modal">
    {this.props.children}
    <button onClick={this.props.onClose}>Close</button>
</div>