JSFiddle - React, Tailwind, and code Playground

HTML

<html>
  <head>
    <script src="https://cdn.jsdelivr.net/npm/vue@2"></script>
  </head>
</html>
<body>
  <div id="app">
    <button v-on:click="myFunc">click !</button>
  </div>
</body>

JavaScript

var app = new Vue({
	el:'#app',
  data(){
  	return{
    	a:null
    }
  },
  methods:{
  	myFunc(){
    
    	new Promise(function(resolve,reject){
      	setTimeout(function(){
        	//
          resolve();
        },1000)
      })
      .then(function(){
      	this.a = 10;
      });
      console.log(this.a)
    }
  },

});