el-tree 替换三角图标

<template>
  <div class="hello">
    <el-tree :data="data" :props="defaultProps" @node-click="handleNodeClick"></el-tree>
  </div>
</template>
<script>
export default {
  data() {
    return {
      data: [
        {
          label: "一级 1",
          children: [
            {
              label: "二级 1-1",
              children: [
                {
                  label: "三级 1-1-1",
                },
              ],
            },
          ],
        },
        {
          label: "一级 2",
          children: [
            {
              label: "二级 2-1",
              children: [
                {
                  label: "三级 2-1-1",
                },
              ],
            },
            {
              label: "二级 2-2",
              children: [
                {
                  label: "三级 2-2-1",
                },
              ],
            },
          ],
        },
        {
          label: "一级 3",
          children: [
            {
              label: "二级 3-1",
              children: [
                {
                  label: "三级 3-1-1",
                },
              ],
            },
            {
              label: "二级 3-2",
              children: [
                {
                  label: "三级 3-2-1",
                },
              ],
            },
          ],
        },
      ],
      defaultProps: {
        children: "children",
        label: "label",
      },
    };
  },
  methods: {
    handleNodeClick(data) {
      console.log(data);
    },
  },
};
</script>

<!-- Add "scoped" attribute to limit CSS to this component only -->
<style >
.el-tree-node__expand-icon.expanded {
  -webkit-transform: rotate(0deg) !important;
  transform: rotate(0deg) !important;
}
.el-icon-caret-right:before {
  /* // 加号图片 */
  content: url("../assets/add.png")  !important;
  font-size: 16px;
}
.expanded:before {
  /* // 减号图片 */
  content: url("../assets/cancel.png")   !important;
  font-size: 16px;
}
.is-leaf.el-tree-node__expand-icon.el-icon-caret-right:before {
  content: "" !important;
  font-size: 16px;
}
</style>