element button内部图标动态切换

 <el-button
          class="filter-item"
          style="margin-left: 10px"
          type="primary"
          :icon="showTree?'el-icon-s-fold':'el-icon-s-unfold'"
          plain
          size="mini"
          @click="btnshowGroup"
        >
        {{showTree?'隐藏分组':'显示分组' }}
        </el-button>

在icon这做一个三目判断即可