Export to excel not working when export any json data object

Question

I work on angular 7 app i export data to excel it generate file excel but cannot open it

 

why and how to solve issue

 

my code used as below 

public exportAsExcelFile(json: any[], excelFileName: string): void {
    const worksheet: XLSX.WorkSheet = XLSX.utils.json_to_sheet(json);
    const workbook: XLSX.WorkBook = { Sheets: { 'data': worksheet }, SheetNames: ['data'] };
    const excelBuffer: any = XLSX.write(workbook, { bookType: 'xlsx', type: 'buffer' });
    this.saveAsExcelFile(excelBuffer, excelFileName);
  }
  private saveAsExcelFile(buffer: any, fileName: string): void {
    const data: Blob = new Blob([buffer], {
      type: EXCEL_TYPE
    });
    const today = new Date();
    const date = today.getFullYear() + '' + (today.getMonth() + 1) + '' + today.getDate() + '_';
    const time = today.getHours() + "-" + today.getMinutes() + "-" + today.getSeconds();
    const name = fileName + date + time;
    FileSaver.saveAs(data, name + EXCEL_EXTENSION);
  }
 getDataByRevision(RevId : any)
  {

   console.log(this.reportdetailslist);
   this.exportAsExcelFile(this.reportdetailslist,'datarevision');
  }

it download and generate file excel but it is not open

 

I think problem on excel it self so i open new angular app and export to excel

 

it is ok exporting without any issue

 

this meaning i have some issue on my code above

 

can you help me please  

 

Excel generating attached with post or thread