title: why ui.item.attr("id") return undefined value?
body: <p>I am working with sortable between <code>&lt;li&gt;</code> of <code>&lt;ul&gt;</code> but when I try to get <code>ui.item.attr("id")</code> I got undefined but other variable are working well like <code>$(this).attr('id')</code> and <code>'+ui.sender.attr('id')</code> but I am searching the index of the <code>&lt;ul&gt;</code> where the element dragged from.</p>
  
  <p>my js file :</p>
  
  <pre><code> $( init );
        function init() {
  
              $(".list-items").sortable({
                   connectWith: '.list-items',
                   items: "li:not(.item.new)",
                   placeholder: 'place-holder',
                   scroll: false,
                   tolerance: "pointer",update: function (event, ui) {
                   //alert($(this));
              }, 
              receive : function(e, ui) { 
                   alert('zone : '+ ui.item.attr("id"));            
  
                   alert('Where the item is dropped : '+$(this).attr('id')); // Where the item is dropped
                   alert('from where the item is dragged : '+ui.sender.attr('id')); // from where the item is dragged
  
                   if(ui.item.text()=="51173115") {
  
                        jConfirm('item '+ui.item.context.id+' capacite Cuisson epuise vous voulez continue comme meme ?', 'alerte', function(r) {     
                    if(r)           
                    {
  
                    }
                    else
                    {
                         $(ui.sender).sortable('cancel'); // refuse element to be dropped
                    }
             }
        }
  
   }).disableSelection();
  
          }
  </code></pre>
  
  <p>my jsf code :</p>
  
  <pre><code>&lt;div class="gauchedragdrop"&gt; 
  
          &lt;p class="ui-widget-header" style="margin:0;padding:5px;color: #2779bb;"&gt;tableof&lt;/p&gt;
            &lt;ul id="ulgauche" class="list-items ui-sortable " &gt; 
              &lt;ui:repeat value="#{gestionduplanning.listzp01Equipe}" var="vari" &gt;
                      &lt;li class="item"&gt;&lt;a  title="#{vari.ordre.toString()}"&gt;#{vari.ordre.toString()}&lt;/a&gt;&lt;/li&gt;
              &lt;/ui:repeat&gt;            
            &lt;/ul&gt;    
  &lt;/div&gt; 
  &lt;div class="droitedragdrop"&gt;
  
              &lt;p:dataTable var="op" value="#{ gestionduplanning.EQlistoneequipe.get(0).listop}" style="width: 700px;float: left;"&gt;
  
                  &lt;p:column headerText ="les of" style="width:550px;"&gt; 
                         &lt;ul id="uldroite" class="list-items ui-sortable"&gt;  
                          &lt;ui:repeat value="#{op.orderedOf}" var="vari" &gt;  
                              &lt;li class="item"  &gt;&lt;a  title="#{vari}"&gt;#{vari}&lt;/a&gt;&lt;/li&gt;
                          &lt;/ui:repeat&gt;                        
                          &lt;/ul&gt; 
                  &lt;/p:column&gt;
                 &lt;/p:dataTable&gt;
  
          &lt;/div&gt;
  </code></pre>
  
  <p>why i get undefined value and how can I get this value ?</p>