JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.6.10/vue.min.js"></script>
<div id="app">
  <div class="block" :class="{ active: isActive }"></div>
  <button @click="isActive = !isActive">Click</button>
</div>

CSS

.block {
  width: 100px;
  height: 100px;
  background: blue;
}
.active {
  background: pink;
}

JavaScript

new Vue({
  el: '#app',
  data: {
    isActive: false
  }
})