script.js

async () => {

  document.addEventListener('click', function (event) {
    let tagItem = event.target.closest('.m5dd_list')
    if (tagItem) {
      if (tagItem.classList.contains('use')) {
        tagItem.classList.remove('use')
      } else {
        tagItem.classList.add('use')
      }
      document.querySelector('#m5dd_result textarea').value = Array
        .from(document.querySelectorAll('.m5dd_list.use>span:nth-child(1)'))
        .map(v => v.innerText)
        .join(', ')
    } else {
      return
    }
  })

}