之前没留档，时间太久忘记了遇到又琢磨半天 尤其是原生的。就此记录下

$('#滑动容器ID').scroll(function(event) {
  var scrollTop = event.currentTarget.scrollTop;
  var scrollHeight = event.currentTarget.scrollHeight;
  var clientHeight =event.currentTarget.clientHeight;
  if(scrollTop+clientHeight >=scrollHeight) {
    $('.js-purchase-btn').removeClass('disabled');
  }
});