$(document).ready(function() {
  $("#scroll_div").scroll(function(){
    alert()
    var divHeight = $(this).height();
    var nScrollHeight = $(this)[0].scrollHeight;
    var nScrollTop = $(this)[0].scrollTop;
    $("#input1").val(nScrollHeight);
    $("#input2").val(nScrollTop);
    $("#input3").val(divHeight);
    if(nScrollTop + divHeight >= nScrollHeight) {
      alert("到达底部了");
    }
  });
});