var app = new Vue({
  el: '#app',
  data: {
    message: "Hello World"
  }
});
setTimeout(function() {
  app.message = "Goodbye World";
}, 2000)


<div id="app">
  <!--Renders as "Hello World"...-->
  <!--Then after 2 seconds re-renders as "Goodbye World"-->
  {{ message }}
</div>