title: Why fadeIn doesn't work?
body: <p>I'm trying to fade in from 0.5 opacity to 1.0 opacity. But it doesn't work.</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>$(document).ready(function(){
  var r = $(".box");r.css({ "opacity":"0.5"});r.text("Box!");r.fadeIn(400);
  })</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"&gt;&lt;/script&gt;
  &lt;div class="box"&gt;&lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>But fading out from 0.5 opacity to 0 works:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>$(document).ready(function(){
  var r = $(".box");r.css({ "opacity":"0.5"});r.text("Box!");r.fadeOut(400);
  })</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"&gt;&lt;/script&gt;
  &lt;div class="box"&gt;&lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>Why is it?</p>