multipleSheetDemo.js

import { LightningElement } from 'lwc';
import { loadScript } from 'lightning/platformResourceLoader';
import workbook from '@salesforce/resourceUrl/JSExcel';
import { ShowToastEvent } from 'lightning/platformShowToastEvent';

export default class FullProfileDetailTab extends LightningElement {

    connectedCallback() {
        // Load the exceljs library as a static resource
        Promise.all([loadScript(this, workbook + "/exceljs/dist/exceljs.js")])
            .then(() => {
                console.log('Library loaded successfully');
            }).catch(error => {
                console.error('Error loading library: ' + JSON.stringify(error));
            });
    }

    // ... (Other helper methods, if any)

    exportExcelData() {
        // Create a new Excel workbook
        const workbook = new ExcelJS.Workbook();

        // ... (Sheet creation logic for 'Index', 'Sheet 1', 'Sheet 2', 'Sheet 3')

        // Write the workbook to a buffer and initiate download
        workbook.xlsx.writeBuffer().then(buffer => {
            var link = document.createElement("a");
            link.href = 'data:application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;base64,' + buffer.toString('base64');
            link.download = 'FullProfileDetails.xls';
            document.body.appendChild(link);
            link.click();
            document.body.removeChild(link);
        });

        // Show success message
        const evt = new ShowToastEvent({
            title: 'Download Successful',
            message: 'Multiple Sheet Data downloaded successfully',
            variant: 'success',
            mode: 'dismissable'
        });
        this.dispatchEvent(evt);
    }
}