vue-event-3.html

<div id="counter-app" style="text-align: center">
  <h3>{{ counter }}</h3>
  <span>
    Increment by <input type="number" v-model="increment" />
  </span>
  <button v-on:click="counter += parseInt(increment)">Count up!</button>
</div>

<script src="https://cdn.jsdelivr.net/npm/vue"></script>
<script>
  new Vue({
    el: '#counter-app',
    data: { counter: 0, increment: 1 }
  });
</script>