// bs4 CSS
loadjs(['https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css'], { target: iframeWin });

// jQuery + bs4 Javascript
loadjs(['https://code.jquery.com/jquery-3.4.1.min.js', 'https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js', 'https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js'], 'core-preview', { async: false, target: iframeWin });