title: Add custom property to vuejs component
body: <p>How do I set a custom property inside a vue component?</p>
  
  <pre><code>var myComponent = Vue.extend({
      data: function() {
          return {
              item: {}
          }
      },
  
      created: function() {
          // This does not seem to work
          this.item.customProperty = 'customProperty';
      }
  });
  </code></pre>