React State

import React, { Component } from 'react';
import ModalWindow from './ModalWindow';

class Modal extends Component {
  constructor() {
    super();
    
    this.state = {
      isOpen: false,
    }
   
  }
  
  handleModal() {
    this.setState({
      isOpen: !isOpen
    }); 
  }
  
  render() {
    const { isOpen } = this.state;
    const modalCls = isOpen ? 'active' : '';
    return(
      <button onClick={() => handleModal()}>Open Modal</button>
      <ModalWindow className={modalCls} />
    );
  }
  
  
}