<script src="http://www.polymer-project.org/polymer.min.js"></script>

<polymer-element name="tag-name" attributes="" constructor="">

  <template>

    <style>

      @host {

        :scope { /* Default styles for the element. */

          display: block;

        }

      }

    </style>

    <div>Shadow DOM content</div>

    <content></content>

  </template>

  <script>

Polymer('tag-name', {

  created: function() {

    this.setAttribute('test', 'wow');

  },

  attributeChanged: function(attrName, oldVal, newVal) {

    //var newVal = this.getAttribute(attrName);

    console.log(attrName, 'old: ' + oldVal, 'new:', newVal);

    alert('newVal: '+newVal);

  }

});

  </script>

</polymer-element>

​

<tag-name></tag-name>

​