import * as Excel from 'exceljs';
import * as fs from 'fs';  

  const stream = fs.createWriteStream(
    `${FilePath}`,
    {
      flags: 'a',
    }
  );
const DefaultColumns = [
    'Col1',
    'Col2',
    'Col3',
    'Col4',
    'Col5',
  ];

  const placeHolders = new Array(DefaultColumns.length);
  const workbook = new Excel.Workbook();
  workbook.created = new Date();
  workbook.modified = new Date();

  const sheet = workbook.addWorksheet('sheet 1', {
    //Also not sure what this is supposed to show
    //No difference if datavalidation condition is failed
    pageSetup: { errors: 'dash' },
  });

  const headerRow = sheet.addRow(DefaultColumns);
  headerRow.eachCell((cell, rowNum) => {
    //@ts-ignore  Typing is wrong
    cell.note = `This is ${rowNum}`;
    //Doesn't do anything
    cell.protection = { locked: true };
  });

  //Also doesn't do anything
  headerRow.protection = { locked: true };
  headerRow.commit();

await workbook.xlsx.write(res);