Bootstrap Animate Navbar on Scroll

Bootstrap Navbar animation: hides navbar on scroll down and shows navbar on scroll up...

HTML

<script src="http://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/2.1.0/bootstrap.min.js"></script>
<nav id="top" class="navbar navbar-default navbar-fixed-top slideDown">
      <div class="container">
        <div class="navbar-header">
          <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar" aria-expanded="false" aria-controls="navbar">
            <span class="sr-only">Toggle navigation</span>
            <span class="icon-bar"></span>
            <span class="icon-bar"></span>
            <span class="icon-bar"></span>
          </button>
          <a class="navbar-brand" href="#">Project name</a>
        </div>
        <div id="navbar" class="navbar-collapse collapse">
          <ul class="nav navbar-nav">
            <li class="active"><a href="#">Home</a></li>
            <li><a href="#about">About</a></li>
            <li><a href="#contact">Contact</a></li>
            <li class="dropdown">
              <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-expanded="false">Dropdown <span class="caret"></span></a>
              <ul class="dropdown-menu" role="menu">
                <li><a href="#">Action</a></li>
                <li><a href="#">Another action</a></li>
                <li><a href="#">Something else here</a></li>
                <li class="divider"></li>
                <li class="dropdown-header">Nav header</li>
                <li><a href="#">Separated link</a></li>
                <li><a href="#">One more separated link</a></li>
              </ul>
            </li>
          </ul>
          <ul class="nav navbar-nav navbar-right">
            <li><a href="../navbar/">Default</a></li>
            <li><a href="../navbar-static-top/">Static top</a></li>
            <li class="active"><a href="./">Fixed top <span class="sr-only">(current)</span></a></li>
          </ul>
        </div><!--/.nav-collapse -->
      </div>
    </nav>
<nav id="bottom" class="navbar...

CSS

@import url('http://getbootstrap.com/dist/css/bootstrap.css');
body {
    background-color: #abc;
    
    color:#FFF;
}



.navbar{
    min-height:0px;
    height: 50px;
    overflow:hidden;
    transition: all .5s;
}

#top.slideDown{
    top:0px;
}

#top.slideUp{
     top:-50px;   
}

#bottom.slideDown{
 top:50px;   
}

#bottom.slideUp{
     top:0px;   
}


#bottom{
    background:black;
    color:white;
}

.shrink {
  height: 0px;
    position:absolute;
    top:0px;
  
}

JavaScript

var scroll = 0;
var hidden = false;
var animating = true;


$(window).scroll(function(e) {
  if ($(document).scrollTop() > scroll && !hidden ) {
     hidden = true;
      $('#top, #bottom').removeClass('slideDown').addClass('slideUp');
  }
  else if(hidden && $(document).scrollTop() < scroll){
     hidden = false;
         $('#top, #bottom').removeClass('slideUp').addClass('slideDown');
  }

scroll = $(document).scrollTop();
 
   
});