z_element_plus/docs/examples/tree/custom-leaf.vue

<template>
  <el-tree :props="props" :load="loadNode" lazy show-checkbox />
</template>

<script lang="ts" setup>
import type Node from 'element-plus/es/components/tree/src/model/node'

interface Tree {
  name: string
  leaf?: boolean
}

const props = {
  label: 'name',
  children: 'zones',
  isLeaf: 'leaf',
}

const loadNode = (node: Node, resolve: (data: Tree[]) => void) => {
  if (node.level === 0) {
    return resolve([{ name: 'region' }])
  }
  if (node.level > 1) return resolve([])

  setTimeout(() => {
    const data: Tree[] = [
      {
        name: 'leaf',
        leaf: true,
      },
      {
        name: 'zone',
      },
    ]

    resolve(data)
  }, 500)
}
</script>