<style lang="css" scoped>
    .aa{
        transition: all 2s;
    }
    .go{
        transform:rotate(-180deg);
        transition: all 2s;
    }
</style>
<template>
<div>
    <i :class="[rotate?'fa fa-arrow-down go':'fa fa-arrow-down aa']" @click="start"></i> //class随rotate的true或者false改变 我这为图方便用了项目里的图标测试，图片也是一样的~
</div>

</template>
<script>
export default {
  data () {
    return {
        rotate:false
    }
  },
  methods: {
      start(){
          this.rotate=!this.rotate;
          console.log(this.rotate)
      }
  }
}
</script>