Observer example inside list.html

list.html

<script>
    Polymer({
      is: 'polymaiap-list',

      properties: {
        data: {
          type: Object,
          observer: '_handleResponse'
        },

        selectedItem: {
          type: Object,
          observer: '_handleSelection'
        }
      },

      //Once data is received via ajax and stored in the data property, loader is hidden and employees list is shown
      _handleResponse: function() {
        this.$.loader.style.display = 'none';
        this.$.listWrapper.style.display = 'block';
      },

      _handleSelection: function() {
        if (this.selectedItem) {
          this.fire('selectedItem', this.selectedItem);
          // Deselect previous selected item to ensure navigation between list and detail
          this.$$('iron-list').deselectItem(this.selectedItem);
        }
      }
    });
  </script>