Google-Apps-Script-Multiple-Column-Multiple-Dropdown-Select.html

<!DOCTYPE html>
<html>
  <head>
    <base target="_top">
  </head>
  <body>
    <div id="checkboxes"></div>
    <button onclick="submit()">Submit</button>
    
    <script>
      google.script.run.withSuccessHandler(function(items) {
        var container = document.getElementById('checkboxes');
        items.forEach(function(item) {
          var checkbox = document.createElement('input');
          checkbox.type = 'checkbox';
          checkbox.id = item;
          checkbox.value = item;
          
          var label = document.createElement('label');
          label.htmlFor = item;
          label.appendChild(document.createTextNode(item));
          
          container.appendChild(checkbox);
          container.appendChild(label);
          container.appendChild(document.createElement('br'));
        });
      }).getItems();
      
      function submit() {
        var selectedItems = [];
        var checkboxes = document.getElementById('checkboxes').querySelectorAll('input[type=checkbox]:checked');
        checkboxes.forEach(function(checkbox) {
          selectedItems.push(checkbox.value);
        });
        
        google.script.run.writeToSheet(selectedItems);
        google.script.host.close();
      }
    </script>
  </body>
</html>