<nav>
  <div class="container">
    <a href="#" id="brand">Brand</a>
    <button>
      <span></span>
      <span></span>
      <span></span>
    </button>
    
    <ul class="navbar-menu">
      <li><a href="#">Home</a></li>
      <li><a href="#">page a</a></li>
      <li><a href="#">page b</a></li>
      <li><a href="#">page c</a></li>
      <li><a href="#">page d</a></li>
    </ul>
    
  </div>
</nav>

body
  background: #eee
  min-height: 3000px
  padding: 0
  margin: 0
  font-family: 'Open Sans', sans-serif

.container
  width: 80%
  margin: 0 auto
  clear: both
  
a
  display: inline-block
  color: #333
  text-decoration: none
  
  
nav
  background: #fff
  height: 80px
  line-height: 80px
  box-shadow: 1px 1px 1px rgba(0, 0,0, 0.2)
  position: fixed
  top: 0
  left: 0
  width: 100%
  z-index: 9998
  transition: all 0.5s
  &.scrollUp
    transform: translateY(-80px)
  
  ul.navbar-menu
    margin: 0
    padding: 0
    display: inline-block
    float: right
    
    li
      display: inline-block
      margin: 0 10px
      a
        color: #666
        font-size: 14px
        
  a#brand
    text-transform: uppercase
    foat: left
    font-weight: 800
    font-size: 20px
    
  button
    background: none
    width: 30px
    height: 40px
    margin-top: 20px
    border: none
    float: right
    display: inline-block
    cursor: pointer
    display: none

    span
      width: 30px
      height: 40px
      height: 2px
      background: #333
      display: block
      margin: 5px 0
      
    

@media (max-width: 768px)
  nav ul.navbar-menu
    display: none
  nav button
    display: block
    
    
    
    

$(document).ready(function () {
  
  'use strict';
  
   var c, currentScrollTop = 0,
       navbar = $('nav');

   $(window).scroll(function () {
      var a = $(window).scrollTop();
      var b = navbar.height();
     
      currentScrollTop = a;
     
      if (c < currentScrollTop && a > b + b) {
        navbar.addClass("scrollUp");
      } else if (c > currentScrollTop && !(a <= b)) {
        navbar.removeClass("scrollUp");
      }
      c = currentScrollTop;
     
     console.log(a);
  });
  
});