javascript - 如何找到滚动条终点释放

Question

一旦用户开始从窗口底部滚动页面，我将尝试删除固定类。下面是我写的代码。但是一旦滚动条到达页面顶部，它就会工作

$(window).scroll(function() {
  if ($(this).scrollTop() > 1){
    $('.sticky-header').addClass('fixed');
  } else{
    $('.sticky-header').removeClass('fixed');
  }
});

Answer 1

您需要跟踪上一个滚动位置，以便知道滚动方向是向上还是向下。

var lastScroll = 0;

$(window).scroll(function() {
  var scrollTop = $(this).scrollTop();
  if (scrollTop == 0 || scrollTop < lastScroll) {
    $('.sticky-header').removeClass('fixed');
  } else {
    $('.sticky-header').addClass('fixed');
  }
  lastScroll = scrollTop;
}).triggerHandler('scroll');

.sticky-header {
  min-height: 500vh;
  border: 1em solid #ccc;
}

.sticky-header:before {
  top: 2em;
  left: 2em;
  padding: 1em;
  background: #eee;
  border: 1px solid #999;
  position: fixed;
  content: 'No fixed class';
}

.sticky-header.fixed:before {
  content: 'With fixed class';
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.2.4/jquery.min.js"></script>

<div class="sticky-header"></div>