Bootsrap Hamburger Menu Jquery

I have created a Bootstrap navbar and would like it so that when the webpages is displayed on a phone the navbar still works. As it currently is the button appears but nothing happens when you click on it. I have taken a look at Code Pen (http://ift.tt/1H67PvM) but their example doesnt work either.

<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="true" 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" >Leeds Market</a>
        </div>
        <div id="navbar" class="collapse navbar-collapse">
          <ul class="nav navbar-nav">
            <li class="active"><a href="homepage.php">Home</a></li>
            <li><a href="about.php">About</a></li>   
            <li><a href="stalls.php">Stalls</a></li>
            <li><a href="products.php">Products</a></li>
            <li><a href="basket.php">Basket</a></li>
          </ul>
          <form class="navbar-form navbar-right" method="post" action="loginsql.php" >
            <div class="form-group">
              <input type="text" placeholder="Username" name="Username" class="form-control">
            </div>
            <div class="form-group">
              <input type="password" placeholder="Password" name="Password" class="form-control">
            </div>
            <button type="submit" class="btn btn-success">Sign in</button>
            <a href="register.php" class="btn btn-success" role="button">Register</a>
      <a href="traderlogin.php" class="btn btn-success" role="button">Trader</a>
          </form>
        </div><!--/.navbar-collapse -->
      </div>
    </nav>