I am facing an issue while merging the cells using ExcelJS, below is the code where I want to merge the cells from B1 to C1, instead of merging the cell it duplicates the value of B1 into C1. See the attached screenshot:

 async getProjectReport(data) {
    try {
      // Create a new workbook and add a worksheet for the report
      const workbook = new ExcelJS.Workbook();
      const worksheet = workbook.addWorksheet('Project Report');

      // Add headers for the project data table
      worksheet.addRow(['Project No.', 'Project Name']).font = {
        bold: true,
      };

      // merge cells
      worksheet.mergeCells('B1:C1');

      // Set column widths for the project data table
      worksheet.columns = [{ width: 12 }, { width: 30 }, { width: 15 }];

      const projectDetailsRow = worksheet.addRow(['1', 'Project Abc']);

      // Write the workbook to a buffer and return it
      const buffer = await workbook.xlsx.writeBuffer();
      return buffer;
    } catch (error) {
      throw new Error(error);
    }
  }

I want a output like the attached screenshot.

I also tried the below function to achieve the output I want but got the same result.

// merge by start row, start column, end row, end column (equivalent to K10:M12)
worksheet.mergeCells(1,2,2,3);