SOURCE

var Main = {
      data() {
        return {
          x: 2,
    			y: 3
        }
      },
  		computed:{
        sum1(){
          return this.x + this.y
        }
      },
      asyncComputed: {
        sum () {
          const total = this.x + this.y
          return new Promise(resolve =>
            setTimeout(() => resolve(total), 1000)
          )
        }
      }
    }
var Ctor = Vue.extend(Main)
new Ctor().$mount('#app')
/*new Vue({
	el: '#app',
  data() {
        return {
          x: 2,
    			y: 3
        }
	 },
    computed:{
      sum1(){
        return this.x + this.y
      }
    },
    asyncComputed: {
      sum () {
        const total = this.x + this.y
        return new Promise(resolve =>
          setTimeout(() => resolve(total), 1000)
        )
      }
    }
});
*/

<script src="//unpkg.com/vue/dist/vue.js"></script>
<script src="//unpkg.com/element-ui@1.2.6/lib/index.js"></script>
<script src="https://unpkg.com/vue-async-computed"></script>
<div id="app">
  <template>
    asyncComputed:{{sum}}
    <br>
    Computed:{{sum1}}
  </template>
</div>

@import url("//unpkg.com/element-ui/lib/theme-default/index.css");