How can I calculate last day as a date in node jst?

I run the script include data of yesterday. i wanna change it.the last day of month i have issue. for example Date:1-4-2022 but the script include data of yesterday we need the file name is :Example_March

how can i define it in this code

 const curMonth = new Date().toLocaleString("default", { month: "long" });

  let fileName = `example_${curMonth}.xlsx`;
  

  writeInFileAsync(html, fileName).then(() => {
    sendEmail(htmlForEmail, fileName);

)}

and save the sheet its the same issue.

const convertJsonToExcel = (table, fileName) => {
  var wb = XLSX.utils.table_to_book(table, {
    sheet: `example_${new Date().getMonth() + 1}`,
    
  });

  XLSX.writeFile(wb, fileName, { cellStyles: true });
};