vue 选中添加样式变色

 <li
              v-for="(item, index) in 15"
              @click="clickcategory(index)"
              :class="{ active: categoryIndex == index }"
            >
              {{ index }}
            </li>

 return {
      
      categoryIndex: 0,
    };

clickcategory(index) {
      // 这里我们传入一个当前值
      this.categoryIndex = index;
    },

li {
        height: 40px;
        line-height: 40px;
         100%;
        &.active {
          background: #e6f7ff;
          border-right: 3px solid #1890ff;
        }
      }