JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.4.2/vue.js"></script>
<div id="simulator">
  <c-simulator-form v-bind:subject="asker"></c-simulator-form>
</div>

JavaScript

Vue.component('c-simulator-form', {
  props: ['subject'],
  template: '<div class="c-simulator-form">{{thesize}}</div>',
  computed: {
    thesize: function() {
      return this.subject.b;
    }
  }
});

var vm = new Vue({
  el: '#simulator',
  data: {
    asker: {
      a: 1,
      b: 2
    }
  }
});

vm.asker['b'] = 4;