JS 原生JS 判断滚动条滑动到底部（兼容苹果safari）

  ListenerScoller () {
    var pageIndex = 1;
    var startX, startY; 
    document.addEventListener('touchstart',function (ev) { 
      startX = ev.touches[0].pageX; 
      startY = ev.touches[0].pageY; 
    }, false); 


    let _this = this;
    document.addEventListener('touchend',function (ev) {
      var endX, endY; 
      endX = ev.changedTouches[0].pageX; 
      endY = ev.changedTouches[0].pageY; 
      var dy = startY - endY;
      var reach = Boolean;
      var scrollTop = document.documentElement.scrollTop || window.pageYOffset || document.body.scrollTop;

      console.log(scrollTop); 
      document.documentElement.scrollHeight == document.documentElement.clientHeight ||   ListenerScoller () {
    var pageIndex =