code: function taskCounterExtension(editor) {
    editor.getTaskCount = () => {
      let found, count;
  
      if (editor.isViewer()) {
        count = editor.preview.$el.find('.task-list-item').length;
      } else if (editor.isMarkdownMode()) {
        found = editor.mdEditor.getValue().match(FIND_TASK_RX);
        count = found ? found.length : 0;
      } else {
        count = editor.wwEditor.get$Body().find('.task-list-item').length;
      }
  
      return count;
    };
  
    editor.getCheckedTaskCount = () => {
      let found, count;
  
      if (editor.isViewer()) {
        count = editor.preview.$el.find('.task-list-item.checked').length;
      } else if (editor.isMarkdownMode()) {
        found = editor.mdEditor.getValue().match(FIND_CHECKED_TASK_RX);
        count = found ? found.length : 0;
      } else {
        count = editor.wwEditor.get$Body().find('.task-list-item.checked').length;
      }
  
      return count;
    };
  }
docs: task counter extension
  @param {Editor} editor - editor instance
  @ignore