title: $(window).scrollTop(value) is not working properly
body: <h3>First</h3>
  
  <pre><code>$(window).scrollTop(value);  // this does not work at first fire. after first, it works well.
  </code></pre>
  
  <h3>second</h3>
  
  <pre><code>setTimeout(function(){
      $(window).scrollTop(scrollVal); // this works well
  }, 100);
  </code></pre>
  
  <p>I can't understand why the first one is not working properly :(
  Is there anyone who know this phenomenon?</p>
  
  <p>thanks for reading. </p>