transparent nav bar to black nav bar on scroll

HTML

<nav class="navbar navbar-inverse navbar-fixed-top">
      <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="#">JO Project</a>
        </div>
        <div id="navbar" class="collapse navbar-collapse">
          <ul class="nav navbar-nav">
            <li><a href="#part1">Part 1</a></li>
            <li><a href="#part2">Part 2</a></li>
            <li><a href="#part3">Part 3</a></li>
            <li><a href="#part4">Part 4</a></li>
          </ul>
        </div><!--/.nav-collapse -->
      </div>
    </nav>

JavaScript

$(document).ready(function(){
    $(window).scroll(function(){
        if($(window).scrollTop() > $(window).height()){
            $(".navbar").css({"background-color":"transparent"});   
        }
    })
})