document.getElementById('generate').onclick = function () {
    var element = document.getElementById('element-to-print');
    var opt = {
    margin:       0.5,
    filename:     '@pdf_filename',
    pagebreak:    { mode: 'avoid-all' },
    image:        { type: 'jpeg', quality: 0.98 },
    jsPDF:        { unit: 'in', format: 'letter', orientation: 'portrait' }
html2pdf().from(element).set(opt).toPdf().get('pdf').then((pdf) => {
    var totalPages = pdf.internal.getNumberOfPages();
    for (i = 1; i <= totalPages; i++) {
        pdf.setPage(i);