example code for https://github.com/natergj/excel4node/issues/268#issuecomment-482634192

merging cells

async function excelDataFiller(rowNumber) {
  const startIndex = 2;
  const j = rowNumber + 1;
  const numDiff = getCountDiff(storage.allCountResults[rowNumber].csdbCount, storage.allCountResults[rowNumber].esCount);
  const perDiff = (storage.allCountResults[rowNumber].csdbCount - storage.allCountResults[rowNumber].esCount) / storage.allCountResults[rowNumber].csdbCount;

  /* Column parameters */
  ws.column(1).setWidth(30);
  ws.column(2).setWidth(27);

  /* Header */

  ws.cell(2, 1).string('Institution').style(styles.header),
  ws.cell(2, 2).string('CD Select').style(styles.header),
  ws.cell(2, 3).string('CSDB').style(styles.header),
  ws.cell(2, 4).string('CD').style(styles.header),
  ws.cell(2, 5).string('Diff').style(styles.header),
  ws.cell(2, 6).string('Variance').style(styles.header),
  ws.cell(2, 7).string('Result').style(styles.header)


  /* Data */
  ws.cell(j + startIndex, 1).string(storage.allCountResults[rowNumber].institutionType),
  ws.cell(j + startIndex, 2).string(storage.allCountResults[rowNumber].selectName),
  ws.cell(j + startIndex, 3).number(storage.allCountResults[rowNumber].csdbCount),
  ws.cell(j + startIndex, 4).number(storage.allCountResults[rowNumber].esCount),
  ws.cell(j + startIndex, 5).number(numDiff),
  ws.cell(j + startIndex, 6).number(perDiff || 0).style(styles.percentage), // If 0 in both counts it returns NaN, so we just write 0 down to the file.
  ws.cell(j + startIndex, 7).string(storage.allCountResults[rowNumber].testStatus)
}

async function excelFileGenerator() {
  // Move this out of your excelDataFiller function.
  ws.cell(1, 1, 1, 7, true).date(new Date());

  for (let i = 0; i < storage.allCountResults.length; i++) {
      // await the completion of excelDataFiller on each iteration
      await excelDataFiller(i)
  }
  wb.write('ConnectedDataCounts.xlsx');
}