add_second_button.js

var $oldList = $('.download-list');
var $nowList = $oldList.clone();
var $laterList = $oldList.clone();

var $style = $('<style>' 
  + '.download-list {' 
  +   'float:left;'
  + '}'
  + '.download-list:first-of-type {'
  +   'margin-right: 30px;'
  + '}'
  + '@media (max-width: 600px) {'
  +   '.download-list {'
  +     'width: 100%;'
  +   '}'
  + '}'
+ '</style>');

$('body').append($style);

$nowList.find('.download-title').each(function() {
	$(this).text('Download Now');
});

$laterList.find('.download-title').each(function() {
	$(this).text('Download Later');
});
$laterList.find('.download-link').each(function() {
	$(this).attr('href', 'https://www.mozilla.org/newsletter/firefox/');
  $(this).addClass('second-button');
});

var $buttonDiv = $('<div class="section"></div>');

$buttonDiv.append($nowList);
$buttonDiv.append($laterList);

$oldList.replaceWith($buttonDiv);