title: jstree: Cannot find element via an attribute
body: <p>I'm trying to select a node according a attribute I have created (db-id) however I have tested with many option and still I don't get the node. Even trying to get the node via the "id" of the tag "li", it doesn't work yet. </p>
  
  <pre><code>$(document).ready(function(){
  $('#jstree').jstree();
  
  $('#jstree').on('ready.jstree', function (e, data) {
      x= $('#jstree').jstree(true).get_node('j1_1');
      alert(x[0].id);
  ...
  </code></pre>
  
  <p>In my example x is null. It seems that because the jstree is generated, it doesn't recognize the dynamic attributes of every "li". Of course I tried many more options like:</p>
  
  <pre><code>node = $('#jstree').find("li[id='j1_1']").closest('li');
  node = $('#jstree').find("li[id='j1_1']");
  node = $('#jstree.jstree-node').find("li[id=j1_1]");
  </code></pre>
  
  <p>but with no good results. Below a small structure of the generated jstree.</p>
  
  <pre><code>&lt;div id="jstree"&gt;
  &lt;ul&gt;
      &lt;li db-id="1459"&gt;AAA004 - low-frequency amplifier
          &lt;ul&gt;
              &lt;li db-id="1460"&gt;AAA005 - power amplifier&lt;/li&gt;
              &lt;li db-id="1461"&gt;AAA006 - voltage amplifier
                  &lt;ul&gt;
                      &lt;li db-id="1462"&gt;AAA007 - differential amplifier
                          &lt;ul&gt;
                              &lt;li db-id="1463"&gt;AAA008 - operational amplifier&lt;/li&gt;
                              &lt;li db-id="1464"&gt;AAA009 - AC-coupled amplifier&lt;/li&gt;
                          &lt;/ul&gt;
                      &lt;/li&gt;
                      &lt;li db-id="1465"&gt;AAA010 - single-sided amplifier&lt;/li&gt;
                  &lt;/ul&gt;
              &lt;/li&gt;
          &lt;/ul&gt;
      &lt;/li&gt;
      &lt;li db-id="1466"&gt;AAA011 - radio frequency amplifier&lt;/li&gt;
      &lt;li db-id="1467"&gt;AAA012 - wideband amplifier&lt;/li&gt;
  &lt;/ul&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>** UPDATE **</p>
  
  <p>The tree above is an example I was testing with.</p>
  
  <p>Using with no $('#jstree').jstree() WORKS!!!...</p>
  
  <pre><code>x= $('#jstree').find("li[db-id='1462']");
  alert(x[0].id);
  </code></pre>
  
  <p>but initializing with $('#jstree').jstree(), the code above works just for the first level but for the rest not anymore. Having said that, in the example, db-id="1459" will works but db-id="1460" wont!!!</p>
  
  <p>Thanks in advance!</p>