// HTML
<div class="hidden" data-contact-btn="true"><button class="btn "><span class="btn-load"></span><span class="text"></span></button></div>

// SASS
.btn-loading
  &::before
    content: ''
    position: relative
    display: inline-block
    vertical-align: top
    width: 18px
    height: 18px
    margin-top: 5px
    margin-right: 10px
    bottom: auto
    left: auto
    opacity: 1
    border-radius: 50%
    border: 3px solid transparent
    border-top: 3px solid rgba(255, 255, 255, 0.7)
    border-right: 3px solid rgba(255, 255, 255, 0.7)
    background: transparent
    animation: 0.5s rotate cubic-bezier(0.4, 0, 0.2, 1) infinite
    +r(992)
      margin-top: 1px
    +r(576)
      margin-top: 0

@keyframes rotate
  from
    transform: rotate(0deg)
  to
    transform: rotate(360deg)

// JS
var contactForm = function() {
    $('.contact-form').each(function() {
      var submit = $(this).find('[type="submit"]');
      var button = $(this).find('[data-contact-btn] button');

      if (submit.length) {
        button.find('.text').html(submit.val());
        submit.replaceWith(button);
        $(this).find('.ajax-loader').remove();
      }
    });

    // Loader
    $('.contact-form form').on('submit', function () {
      var btn = $(this).find('.btn');

      if (btn.hasClass('btn-link')) {
        btn.addClass("btn-loading");
        btn.find('.text').css('display', 'none');
      } else {
        btn.addClass("btn-loading");
      }
    });

    $('.wpcf7').on('wpcf7spam wpcf7invalid wpcf7mailsent wpcf7mailfailed', function (e) {
      var form = $('.contact-form');
      $(form).find('.btn').removeClass("btn-loading");
    });
  };

  contactForm();