用变量同时控制div的class和数据

<div @click="dropDownMenu">
    <i
        :class="{
            'el-icon-arrow-down': !showMore,
            'el-icon-arrow-up': showMore
        }">
    </i>
</div>

....
// script
data () {
        return {
          ...
           showMore: false
        }
 },
computed: {
    showTag () {
        if (this.showMore) {
            return this.data
        } else {
            return this.data.slice(0, 10)
        }
    }
}

....
dropDownMenu() {
    this.showMore = !this.showMore
}