typecho-theme-sagiri/js/modules/mouse.js

Lovely theme for Typecho.

// site-nav animation. for pc
var siteNav = document.querySelector('.site-nav')
var agent = navigator.userAgent

function flag() {
  var scrollHeight =
    document.body.scrollHeight || document.documentElement.scrollHeight
  var clientHeight =
    document.body.clientHeight || document.documentElement.clientHeight
  var canScrollTop = scrollHeight - clientHeight
  return canScrollTop > clientHeight / 2
}

if (/.*Firefox.*/.test(agent)) {
  document.addEventListener(
    'DOMMouseScroll',
    function(e) {
      e = e || window.event
      var detail = e.detail

      if (flag()) {
        if (detail > 0 && scrollTop > 0) {
          siteNav.style.transform = 'translateY(-100%)'
        } else {
          siteNav.style.transform = 'translateY(0%)'
        }
      }
    },
    { passive: true }
  )
} else {
  document.onmousewheel = function(e) {
    e = e || window.event
    var wheelDelta = e.wheelDelta
    if (flag()) {
      if (wheelDelta > 0) {
        siteNav.style.transform = 'translateY(0%)'
      } else {
        siteNav.style.transform = 'translateY(-100%)'
      }
    }
  }
}