[Vuejs]-Property or method "close" is not defined on the instance but referenced during render. Make sure that this property is reactive

success and close functions should be placed inside the methods field in order to be recognized by the template as methods :

 export default {
      name: "app",
      components: {
        OkoButton
      },
  methods:{  
    success: function() {
       window.console.log("oko success");
      },
      close: function() {
        window.console.log("oko closed");
      }
    }
    };