title: AJAX : How to manipulate variable with condition
body: <p>I'm trying to find a solution to this : </p>
  
  <ul>
  <li>I have a  with the attribute "visibility" to hidden (this on the load() event)</li>
  <li>I have a button which execute an SQL operation (file called : requetesql.php)</li>
  <li>requetesql.php file check information in my database and return a name (the image filename).</li>
  </ul>
  
  <p>It works very well BUT ... I would like this : When the SQL returns "nothing", the attribute style.visibility of the  doesn't change and still "hidden".</p>
  
  <p>I tried many things such as :</p>
  
  <ul>
  <li>testing with a condition after '$('#logo').html(content);' like : <code>if (content==''){...]</code> but nothing works.</li>
  </ul>
  
  <p>Any help will be appreciate :)</p>
  
  <p>Thanks dude ! </p>
  
  <p>`function go(){</p>
  
  <pre><code>            $.ajax({
  
  
              url: "requetesql.php",
               ifModified:false,
  
              success: function(content) {
              $('#logo').html(content);
  
                  document.getElementById('logo').style.visibility="visible";
                  document.getElementById('logo_cont').style.visibility="visible";
                  var img = document.createElement("IMG");
                  img.src = 'server/php/files/'+content;
                  document.getElementById('logo').appendChild(img);
  
  
          }
          });`
  </code></pre>