Creating excel file and writing to it with ExcelJS

Solved it by adding array to describe columns in second part of the code. Then the 3rd row was added successfully. When passing an object with column names to addRow() I had to provide a description of columns that already existed in excel file.

const Excel = require('exceljs');async function exTest(){  const workbook = new Excel.Workbook();  const worksheet = workbook.addWorksheet("My Sheet");worksheet.columns = [ {header: 'Id', key: 'id', width: 10}, {header: 'Name', key: 'name', width: 32},  {header: 'D.O.B.', key: 'dob', width: 15,}];worksheet.addRow({id: 1, name: 'John Doe', dob: new Date(1970, 1, 1)});worksheet.addRow({id: 2, name: 'Jane Doe', dob: new Date(1965, 1, 7)});// save under export.xlsxawait workbook.xlsx.writeFile('export.xlsx');//load a copy of export.xlsxconst newWorkbook = new Excel.Workbook();await newWorkbook.xlsx.readFile('export.xlsx');const newworksheet = newWorkbook.getWorksheet('My Sheet');newworksheet.columns = [ {header: 'Id', key: 'id', width: 10}, {header: 'Name', key: 'name', width: 32},  {header: 'D.O.B.', key: 'dob', width: 15,}];await newworksheet.addRow({id: 3, name: 'New Guy', dob: new Date(2000, 1, 1)});await newWorkbook.xlsx.writeFile('export2.xlsx');console.log("File is written");};exTest();

Working link attached

const Excel = require('exceljs');// Create workbook & add worksheetconst workbook = new Excel.Workbook();const worksheet = workbook.addWorksheet('ExampleSheet');// add column headersworksheet.columns = [  { header: 'Package', key: 'package_name' },  { header: 'Author', key: 'author_name' }];// Add row using key mapping to columnsworksheet.addRow(  { package_name: "ABC", author_name: "Author 1" },  { package_name: "XYZ", author_name: "Author 2" });// Add rows as Array valuesworksheet  .addRow(["BCD", "Author Name 3"]);// Add rows using both the above of rowsconst rows = [  ["FGH", "Author Name 4"],  { package_name: "PQR", author_name: "Author 5" }];worksheet  .addRows(rows);// save workbook to diskworkbook  .xlsx  .writeFile('sample.xlsx')  .then(() => {    console.log("saved");  })  .catch((err) => {    console.log("err", err);  });

https://repl.it/@vishwasc/ExcelJs-Example#index.js

image attachemnts

// add image to workbook by filenameconst imageId1 = workbook.addImage({  filename: 'path/to/image.jpg',  extension: 'jpeg',});// add image to workbook by bufferconst imageId2 = workbook.addImage({  buffer: fs.readFileSync('path/to.image.png'),  extension: 'png',});// add image to workbook by base64const myBase64Image = "data:image/png;base64,iVBORw0KG...";const imageId2 = workbook.addImage({  base64: myBase64Image,  extension: 'png',});

Note that in both cases, the extension must be specified. Valid extension values include 'jpeg', 'png', 'gif'.