index.html

<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>example</title>
  <script src="./index.js" charset="utf-8"></script>
  <!--<script src="https://unpkg.com/vue/dist/vue.js" charset="utf-8"></script>-->
</head>
<body>
  <div id="mvvm">
    <h2>{{b}}</h2>
    <input type="text" x-model="a">
    <input type="text" name="" value="" x-model="a">
    <p x-html="a">{{ a }}</p>
    <button type="button" name="button" x-on:click="testToggle">change b</button>
  </div>
</body>
<script>
var vm = new MVVM({
  el: '#mvvm',
  data: {
    a: 'test model',
    b: 'hello MVVM',
    flag: true,
    arr: [1 ,2 ,3],
    obj: {name: "ccc", pwd: 123}
  },
  methods: {
    testToggle: function () {
      this.flag = !this.flag;
      this.b = this.flag ? 'hello MVVM' : 'test success'
    }
  }
});


// var vue = new Vue({
//   el: '#mvvm',
//   data: {
//     a: 'test model',
//     b: 'hello MVVM',
//     flag: true,
//     arr: [1 ,2 ,3]
//   },
//   methods: {
//     testToggle: function () {
//       this.flag = !this.flag;
//       this.b = this.flag ? 'hello MVVM' : 'test success'
//     }
//   }
// });
</script>
</html>