JSFiddle - React, Tailwind, and code Playground

HTML

<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport"
        content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <script src="https://cdn.jsdelivr.net/npm/vue@2.5.16/dist/vue.js"></script>
</head>
<body>
  <div id="app" style="width: 600px;margin: 100px auto;">
    <div>
      arr[0]= {{arr[0]}}
    </div>
    <div v-if="arr[0]">
     arr[0]测试区域
    </div>
    <div>
      obj.a = {{obj.a}}
    </div> 
    <button @click="change">按钮</button>
  </div>
  </body>
</html>

JavaScript

new Vue({
      el: '#app',
      data: {
        arr: [false],
        obj: {
          a: false
        }
      },
      created() {
      },
      methods: {
        change() {
          this.arr[0] = !this.arr[0]
//          console.log(this.arr)
//          Vue.set(this.arr, 0, !this.arr[0])
         this.obj.a = !this.obj.a
        }
      }
    })