Не получается прочитать свойство

class ModalWindow {
  constructor({
    title,
    descr,
    exit,
    htmlContent
  }) {
    this.title = title;
    this.descr = descr;
    this.exit = exit;
    this.htmlContent = htmlContent;
  }

  create() {
    const modal = document.createElement('div'),
      title = document.createElement('h3'),
      descr = document.createElement('div'),
      exit = document.createElement('button'),
      content = document.createElement('div');

    modal.classList.add('modal-window');
    modal.id = 'modalWindow'
    title.classList.add('title');
    descr.classList.add('descr');
    exit.classList.add('exit-btn');
    exit.id = 'exitModal';
    content.classList.add('content');

    title.textContent = this.title.trim();
    descr.textContent = this.descr.trim();
    content.textContent = this.htmlContent.trim();

    modal.appendChild(title);
    modal.appendChild(descr);
    modal.appendChild(exit);
    modal.appendChild(content);

    document.body.appendChild(modal);
  }

  close() {
    const modal = document.querySelector('#modalWindow');
    modal.remove();
  }
}

const settings = {
  title: 'a',
  descr: 'ad',
  exit: 'ad',
  htmlContent: 'ada'
}

function newModalWindow(settings) {
  const modalWindow = new ModalWindow(settings);
  const btn = document.querySelector('#button');
  let exit;

  btn.addEventListener('click', () => {
    modalWindow.create();
    exit = document.querySelector('#exitModal');
  }, {
    capture: true
  });

  exit.addEventListener('click', () => {
    modal.close();
  }, {
    capture: true
  });
}

newModalWindow(settings);

* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}

body {
  position: relative;
}

.modal-window {
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  border: 3px solid rgb(27, 27, 27);
  border-radius: 12px;
  padding: 15px 30px;
  min-height: 500px;
  min-width: 500px;
  text-align: center;
}

.modal-window .exit-btn {
  position: absolute;
  right: 5px;
  top: 5px;
  padding: 5px;
  cursor: pointer;
}

<button id="button"><img src="img/icon.svg" alt="фильтр"></button>