title: onload add class to the document
body: <p>Simply when the page loads I'd like to add a blur to the whole document</p>
  
  <pre><code>    function loading() {
  
      document.getElementById('.header').addClass('loading-style');
  
      setTimeout(function(){}, 3000);
  }
  </code></pre>
  
  <p>and there's <code>&lt;body onload="loading()"&gt;</code></p>
  
  <p>And finally the style :</p>
  
  <pre><code>.loading-style {
      -webkit-filter: blur(5px);
      -moz-filter: blur(5px);
      -o-filter: blur(5px);
      -ms-filter: blur(5px);
      filter: blur(5px);
  }
  </code></pre>