el-cascader对于懒加载有支持方法，小难点在于回显的时候，由于懒加载第一次只有一层，所以要根据选中id数组一层层的加载。

子组件

<template>
  <el-cascader
    ref="cascaderRef"
    v-model="selectedValue"
    :props="CascaderProps"
    :disabled="disabled"
    style="width: 500px"
  />
</template>

  
<script setup>
import { ref, onMounted, defineEmits } from "vue";
import { ElCascader } from "element-plus";
import { listByParent, listParentByChild } from "@/api/common.js";
const cascaderRef = ref();
const props = defineProps({
  modelValue: [String, Number],
  disabled: {
    type: Boolean,
    default: false,
  },
});
const selectedValue = ref([]); // 选中的id数组

const emit = defineEmits(["update"]); // 更新父组件的值
const CascaderProps = {
  lazy: true, // 懒加载
  checkStrictly: true, // 选择任意一项
  lazyLoad(node, resolve) {
    const { level, pathValues } = node;
    listByParent({
      adiId: node.value,
    }).then((res) => {
      const nodes = res.data.map((item) => {
        return {
          ...item,
          label: item.name,
          value: item.adiId,
          leaf:
            (pathValues[0] == "330000000000" && level == 4) ||
            (pathValues[0] != "330000000000" && level == 2)
              ? true
              : false, // 浙江地区层级和别的省层级不一样，true表示最后一层
        };
      });
      resolve(nodes);
    });
  },
};
// 回显逻辑
onMounted(async () => {
  selectedValue.value = []; // 重置
  setTimeout(async () => {
    // 延迟执行
    if (props.modelValue) {
      // 存在值
      let ids = await listParentByChild({
        type: 1,
        childAdiId: props.modelValue,
      }); // 获取父级id数组
      ids = ids.data.map((item) => item.adiId);
      selectedValue.value = ids.reverse(); // 调换顺序，省市区顺序
      await resolveCascaderNodes(selectedValue.value);
    }
  }, 1000);
});

// 递归解析路径
const resolveCascaderNodes = async (ids) => {
  const nodes = [];
  let currentParent = "";
  // 加载子节点路径
  for (const id of ids) {
    const children = await listByParent(currentParent);
    const target = children.data.find((item) => item.id === id);
    if (target) {
      nodes.push(target);
      currentParent = id;
    }
  }
  return nodes;
};
// 监听值变化
watch(selectedValue, (val) => {
  if (val.length) emit("update", val[val.length - 1]);
});
</script>

父组件

                  <AreaCascader
                    :key="new Date().getTime()"
                    :disabled="disabled"
                    :modelValue="form.concatAddress"
                    @update="update"
                  />

key是为了每次使用都刷新，不加不会每次调用onMounted里的方法
form.concatAddress的值是最后一个区划id,在子组件里面要用接口获取到完整的id数组

import AreaCascader from "@/components/Cascader/index.vue";

const update = (val) => {
  form.value.concatAddress = val;
};

记录一下