index.ts

import ExcelJS from 'exceljs'
import Handlebars from 'handlebars';

export default class ExcelHandlebars {
  constructor() { }

  public registerHelper = (name: string, fun: Handlebars.HelperDelegate) => {
    Handlebars.registerHelper(name, fun)
  }

  public async renderExcel(input: string, output: string, data: any) {
    const book = await new ExcelJS.Workbook().xlsx.readFile(input);
    const totalWorksheets = book.worksheets.length
    const worksheetsNames = book.worksheets.map(worksheet => { return worksheet.name })

    for (let sheetIndex = 0; sheetIndex < totalWorksheets; sheetIndex++) {
      const dataSheet = book.getWorksheet(worksheetsNames[sheetIndex]);
      const maxColumns = dataSheet.actualColumnCount //Column is horizonal
      const maxRows = dataSheet.actualRowCount //Row is vertical

      for (let rowIndex = 1; rowIndex <= maxRows; rowIndex++) {
        for (let columnIndex = 1; columnIndex <= maxColumns; columnIndex++) {
          const cell = dataSheet.getRow(rowIndex).getCell(columnIndex)
          if (typeof cell.value == 'string') {
            cell.value = Handlebars.compile(cell.value)(data);
          }
        }
      }

      await book.xlsx.writeFile(output);
    }
  }
}