title: Pass id of element to ng-class directive
body: <p>I look all over but couldn't find a way to get id of element that has 
  a <code>ng-class</code> passed to ng-class function:</p>
  
  <pre><code>&lt;ol ng-controller="PanelController as panel"&gt;
       &lt;li id="IdIWant" ng-class="{active: panel.isSelected(WHAT GOES HERE?)}"&gt;&lt;/li&gt;
       &lt;li id="IdIWant2" ng-class="{active: panel.isSelected(WHAT GOES HERE?)}"&gt;&lt;/li&gt;
       &lt;li id="IdIWant3" ng-class="{active: panel.isSelected(WHAT GOES HERE?)}"&gt;&lt;/li&gt;
  &lt;/ol&gt;
  </code></pre>
  
  <p>and javascript:</p>
  
  <pre><code>app.controller("PanelController", function(){
          this.selectTab = function(setTab){
              this.tab  = setTab;
          };
              this.isSelected = function(checkTab){
                  console.log(checkTab);
                  return this.tab===checkTab;
              }
          });
  </code></pre>
  
  <p><strong>Long story</strong>:<BR>
  In tutorials i get:</p>
  
  <pre><code>&lt;li ng-class="{active: panel.isSelected(1)}"&gt;1&lt;/li&gt;
  &lt;li ng-class="{active: panel.isSelected(2)}"&gt;2&lt;/li&gt;
  &lt;li ng-class="{active: panel.isSelected(3)}"&gt;3&lt;/li&gt;
  </code></pre>
  
  <p>then i can set active class based on the number but i want pass
  number (1,2 or 3) from the id, or ng-data or other way (thus not writing it in <code>panel.isSelected()</code>)<BR>
  like:</p>
  
  <pre><code>&lt;li id="1" ng-data="1" ng-class="{active: panel.isSelected(WHAT GOES HERE?)}"&gt;1&lt;/li&gt;
  </code></pre>