code: function getRowspanNum(data = [], child = []) {
    let childs = [];
    for (let i = 0; i < data.length; i += 1) {
      if (!data[i].children) {
        childs.push(data[i]);
      } else if (data[i].children && data[i].children.length > 0) {
        childs = childs.concat(getRowspanNum(data[i].children, child));
      }
    }
    return childs;
  }
docs: Get rowspan number
  @param {Array} date