jquery - 当另一个 div 在窗口中可见时隐藏元素

Question

当 #pre-footer 或 #footer div 可见时，我需要将类 .hidden 切换到我的粘性菜单 window 。

我一直在搞乱 jquery 和 scrollTop(); 但似乎无法让它继续下去。任何帮助将不胜感激

$(document).ready(function() {
    var $window = $(window);
  var tabwrap = $('.tab-wrap');
  var prefooter = $('#pre-footer');
  $window.on('scroll', function() {
    var scrollTop = $window.scrollTop();
    tabwrap.toggleClass('hidden', scrollTop > 300); /* Help! */
    /* .tabwrap should toggle class .hidden when #pre-footer and or #footer is visible in window */
  });
});

到目前为止的 fiddle :https://jsfiddle.net/gavinfriel/4tcjnoxp/5/

Answer 1

所以基本上你想在视口(viewport)底部与 #pre-footer 底部对齐时切换类。所以当视口(viewport)的scrollTop值+高度大于pre-footer的顶部位置+#pre-footer的高度

$(document).ready(function() {
  var $window = $(window);
  var tabwrap = $('.tab-wrap');
  var prefooter = $('#pre-footer');
  var prefooter_top = prefooter.offset().top;
  var prefooter_height = prefooter.height();
  var prefooter_bottom = prefooter_top + prefooter_height;
  console.log(prefooter_bottom);
  $window.on('scroll', function() {
    var scrollTop = $window.scrollTop();
    var viewport_height = $(window).height();
    var scrollTop_bottom = scrollTop + viewport_height;
    tabwrap.toggleClass('hidden', scrollTop_bottom > prefooter_bottom); 
  });
});