code: function (attrName, oldVal, newVal) {
  
              var property = vcomet.util.hyphenToCamelCase(attrName);
  
              // The onAttributeChanged callback is triggered whether its observed or as a reflection of a property
              if (el.__observeAttributes[attrName] || el.__reflectProperties[property]) {
                  vcomet.triggerAllCallbackEvents(el, config, "onAttributeChanged", [attrName, oldVal, newVal]);
              }
  
              // The onPropertyChanged callback is triggered when the attribute has changed and its reflect by a property
              if (el.__reflectProperties[property]) {
                  el["__" + property] = newVal;
                  vcomet.triggerAllCallbackEvents(el, config, "onPropertyChanged", [property, oldVal, newVal]);
              }
  
          }
docs: Callback to be triggered when the user calls to setAttribute