title: Change class of label element in nput box in angularjs
body: <p>I'm quite new in AngularJS. I'm trying to change the class of a label element while I'm doing something on an input text.</p>
  
  <p>What I have is the following:</p>
  
  <pre><code>&lt;form&gt;
    &lt;input id="first_name" type="text" ng- blur="moveLabelFirstName=!moveLabelFirstName" ng- focus="moveLabelFirstName=!moveLabelFirstName" /&gt;
    &lt;label for="first_name" ng-class="{'active':moveLabelFirstName}"&gt;MyName&lt;/label&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>This adds/remove the class active whenever focus/blur is activated on the input box. What I would like in addition is to add one more class, e.g. onchange, whenever the input is empty or non empty. </p>
  
  <p>I have seen in angular that ng-empty and ng-non-empty are added, but it's on the input and not on the label.</p>
  
  <p>How could I make it?</p>
  
  <p>Thanks</p>