【jQuery】下に固定要素を置くのでフッターの下を自動でズラす

<section class="cta">
  <div class="cta_area">
    <div class="cta_box">
      <a href="https://125naroom.com/web/3982" target="_blank" class="_a">詳しくはこちら</a>
    </div>
  </div>
</section>

.cta {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  width: 100%;
  background-color: rgba(26, 70, 121, 0.8);
  border-top: 3px solid #f30d44;
  z-index: 2;
}
.cta_area {
  padding: 0 30px;
  margin-top: 0.8rem;
  margin-bottom: 0.8rem;
}
.cta_box {
  display: flex;
  justify-content: center;
}

$(function(){
  if( $('.cta') ){
    $(window).on({ 'load': setCta, 'resize': setCta });
    function setCta(){
      $('body').css('padding-bottom', $('.cta').outerHeight());
    }
  }
});