<script>
function printDiv() {
var divContents = document.getElementById("main_div").innerHTML;
var a = window.open('', '', 'height=500, width=500');
a.document.write('<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css"><html>');
a.document.write('<body >');
a.document.write(divContents);
a.document.write('</body></html>');
a.document.close();
a.print();
}
</script>