<template>
<div>
   <button @click="onAddition">加</button>
   <button  @click="onSubtraction">减</button>
   <p> 当前值：{{ count }} </p>
   <p> 双倍值：{{ dounbleCount }}</p>
</div>
</template>

<script>
export default {
  data() {
    return {
     count: 1,
    };
  },
  computed: {
    dounbleCount() {
      return this.count * 2;
    }
  },
  methods: {
    onAddition() {
      ++this.count
    },
    onSubtraction() {
      --this.count
    }
  }
};
</script>