JSFiddle - React, Tailwind, and code Playground

HTML

<div id="app">
  <p>{{ a.number }}</p>
  <button @click="a.number++">increase</button>
</div>

Vue

new Vue({
  el: "#app",
  data: {
    a: {number: 1}
  },
  watch: {
    a: {
      handler() {
        alert("changed")
      },
      deep: true
    }
  }
})