extractData.js

function extractData() {
  const boxes = Array.from(document.querySelector('#boxes').children);
  const result = boxes.map(box => {
    const obj = {
      title: '', 
      subtitle: ''
    }
    for(let item of Array.from(box.children)) {
      if(item.className === 'title') {
        obj.title = item.textContent;
      }
      if(item.className === 'subtitle') {
        obj.subtitle = item.textContent;
      }
    }
    return obj;
  });
  return result;
}
extractData()