<template>
  <div id="app">
    <ul>
      <li v-for="item in list" :key="item">{{item}}</li>
    </ul>
  </div>
</template>
<script>
export default {
  data(){
    return{
      list:['1','2','3']
    }
  },
  mounted(){
      // this.list[0] = '998';
      this.$set(this.list,0,998)
      console.log(this.list)
  }
}
</script>