new Vue({
  el: "#app",
  data: {
    todos: [{
        text: "Learn JavaScript",
        done: false
      },
      {
        text: "Learn Vue",
        done: false
      },
      {
        text: "Play around in JSFiddle",
        done: true
      },
      {
        text: "Build something awesome",
        done: true
      }
    ]
  },
  methods: {
    toggle: function(index) {
      this.todos[index].done = !this.todos[index].done
    }
  }
})

body {
  background: #20262E;
  padding: 20px;
  font-family: Helvetica;
}

#app {
  background: #fff;
  border-radius: 4px;
  padding: 20px;
  transition: all 0.2s;
}

li {
  margin: 8px 0;
}

h2 {
  font-weight: bold;
  margin-bottom: 15px;
}

del {
  color: rgba(0, 0, 0, 0.3);
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <h2>Todos:</h2>
  <ol>
    <li v-for="({text, done}, i) in todos">
      <label>
        <input type="checkbox"
          v-on:change="toggle(i)"
          v-bind:checked="done">

        <del v-if="done">
          {{ text }}
        </del>
        <span v-else>
          {{ text }}
        </span>
        
        {{todos[i]}}
      </label>
    </li>
  </ol>
</div>