How to Create excel file and download it or convert into base64 string

How to Create excel file and download it or convert into base64 string

1).First Install Following packages from Node module

1).npm install exceljs
page Url:https://www.npmjs.com/package/exceljs

2).npm install file-saver --save
page Url:https://www.npmjs.com/package/file-saver

Code Writing:-

import * as Excel from 'exceljs/dist/exceljs';
import * as FileSaver from 'file-saver';
import { Injectable } from '@angular/core';
@Injectable({
  providedIn: 'root',
})
export class HeroService {
  constructor() { }
public generateExcel(paramData: any, _ReferenceNo, IsSend = false): any {
    return new Promise((resolve, reject) => {
  if (IsSend) {
        return this.workbook.xlsx.writeBuffer({
          base64: true
        }).then((data) => {
          const itemdata = new Blob([data], { type: "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" });
          const reader = new FileReader();
          reader.readAsDataURL(itemdata);
          reader.onloadend = function () {
            return resolve(reader.result.toString().replace('data:application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;base64,', ''));
          }
        });

      } else {
        this.workbook.xlsx.writeBuffer().then((data) => {
          const blob = new Blob([data], { type: EXCEL_TYPE });
          FileSaver.saveAs(blob, _ReferenceNo ? _ReferenceNo : 'temporary' + EXCEL_EXTENSION);
          return resolve(data);
        });
      }
});
}

}

Calling Method to component:- 

this.pdfService.generatePDF(this.trademodel, true, false).then(resp=>{
postJson.PdfString=resp;
});