assets/js/nav.js


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var new_scroll_position = 0;
var last_scroll_position;
var header = document.getElementById("nav");

window.addEventListener('scroll', function(e) {
  last_scroll_position = window.scrollY;

  // 向下滚动
  if (new_scroll_position < last_scroll_position && last_scroll_position > 80) {
    header.classList.remove("slideDown");
    header.classList.add("slideUp");

  // 向上滚动
  } else if (new_scroll_position > last_scroll_position) {
    header.classList.remove("slideUp");
    header.classList.add("slideDown");
  }

  new_scroll_position = last_scroll_position;
});