title: Hide / Show header on scroll effect jQuery
body: <p>I'm trying to implement this <a href="https://www.invisionapp.com/" rel="nofollow">https://www.invisionapp.com/</a> header on scroll effect but can't make it work.</p>
  
  <p>I tried this </p>
  
  <pre><code>  jQuery(window).scroll(function () { 
      if (jQuery(this).scrollTop() &lt; 200) {
        jQuery('header').hide();
      } else {
        jQuery('header').show();
      }
    });
  </code></pre>
  
  <p>but it doesn't work. Header doesn't appear. I found some header animations libraries that do this effect, but I want to implement it by simple jQuery code, don't want to use library.   </p>
  
  <p>Can somebody help me please?</p>