CodePen Embed - gOwOdVe

<div id="app">
  <div 
  v-for="(item, index) in 3" 
  :class="'day-' + (index + 1)" 
  v-show="(index + 1) === prop">
  {{index + 1}}
</div>
</div>

new Vue({
  el: "#app",
  data: {
    prop: 3
  },
})

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