ap.hideLoading()

<script src="https://gw.alipayobjects.com/as/g/h5-lib/alipayjsapi/3.1.1/alipayjsapi.inc.min.js"></script>

<button id="J_btn" class="btn btn-default">showLoading</button>
<script>
  var btn = document.querySelector('#J_btn');
  btn.addEventListener('click', function(){
    ap.showLoading({
      content: '2秒后消失',
      delay: 1000
    });
    setTimeout(function(){
      ap.hideLoading();
    }, 3000);
  });
</script>