JavaScript to get `${column title}: ${column card count}` strings on Trello board

getPaneInfo.js

{
  let panes = document.querySelectorAll("div.list-wrapper");
  let alertTextArray = new Array();
  // console.log(panes);
  for (pane of panes) {
    if (!pane.classList.contains("is-idle")){
      let title = pane.getElementsByClassName("list-header-name-assist")[0].innerText;
      // console.log(title);
      let cards = pane.getElementsByClassName("list-card-details");
      // console.log(`${title}: ${cards.length}`)
      let checkedCount = 0;
      for (card of cards) {
        if (card.getElementsByClassName("card-label").length > 0) {
          checkedCount++;
        }
      }
      alertTextArray.push(`${title}: ${cards.length} (${checkedCount} cards are checked)`);
    }
  }
  prompt("copy and paste", alertTextArray.join(`\n`));
}