Downloading data in excel format with Nest.js

1: use :: https://wajihaabid.medium.com/downloading-data-in-excel-format-with-nest-js-4a0a859bf430

excel.controller.ts

import {Controller, Get, Header, Res} from '@nestjs/common';
import { ExcelService } from './excel.service';
import {Response} from "express";

@Controller('excel')
export class ExcelController {
  constructor(private readonly excelService: ExcelService) {}

  @Get('/download')
  @Header('Content-Type', 'text/xlsx')
  async downloadReport(@Res() res: Response) {
    let data  = [
      {
        'name':'ali',
        'lname':'aliii',
      },
      {
        'name':'reza',
        'lname':'rezazzz',
      },
      {
        'name':'hassan',
        'lname':'hassini',
      }
    ];

    let merges = ['A2:A3' , 'B2:B3' ];
    let header  =
                    [
                      'name222',
                      'lname333',
                    ]
                  ;
    let result  = await this.excelService.downloadExcel(header, data, merges);

    res.download(`${result}`);
  }

}

excel.service.ts

import { HttpException, HttpStatus, Injectable} from '@nestjs/common';
import * as tmp from  'tmp';
import {Workbook} from "exceljs";

@Injectable()
export class ExcelService {

    /**
     * downloadExcel
      * @param header
     * @param data
     * @param merges
     */
  async downloadExcel( header: string[]= [], data: object[]= [], merges: string[]= []){
    if( !data.length ){
        throw new HttpException(
            'no data for download',
            HttpStatus.BAD_REQUEST,
        );
    }

    let rows  = [];

    rows.push(header);

    data.forEach( doc=>{
      rows.push(Object.values(doc));
    })

    let book  = new Workbook();

    let sheet =   book.addWorksheet('sheet1' ,{views:[{ rightToLeft: true}]})


    sheet.addRows( rows);

    if(merges.length){
        for(let merge of merges){
            sheet.mergeCells(merge)
        }
    }



    let file = await new Promise( ( resolve, reject) => {
                tmp.file(
                    {discardDescriptor: true, perfix: 'MyExcelSheet', postfix: '.xlsx', mode: parseInt('0600', 8)},
                    async (err, file) => {
                        book.xlsx.writeFile(file).then(_ => {
                            resolve(file);
                        }).catch(err => {
                           throw new HttpException(
                                'data is invalid',
                                HttpStatus.BAD_REQUEST,
                            );
                        })

                    }
                )
            }
        );





    return file;
  }

}