Vue

HTML

<div id="app">
  {{$root.inner[$root.inner.key]}}
</div>

CSS

body {
  background: #20262E;
  padding: 20px;
  font-family: Helvetica;
}

#app {
  background: #fff;
  border-radius: 4px;
  padding: 20px;
  transition: all 0.2s;
}

li {
  margin: 8px 0;
}

h2 {
  font-weight: bold;
  margin-bottom: 15px;
}

del {
  color: rgba(0, 0, 0, 0.3);
}

Vue

APP = new Vue({
  el: "#app",
  data: {
    inner: {
    	key: "key1",
      key1: "value1",
      key2: "value2"
    }
  }
})

APP.inner.key = "key2";