Summary

I learned a lot from this example. After understanding it more deeply, I discovered that if a child item is the only child of its parent item, the parent item should also be deleted after deleting it. The original documentation didn't consider this, and there were many details to pay attention to during implementation. I finally completed it, and I'll post my code below.

Page

https://react.dev/learn/choosing-the-state-structure

Details

import {useImmer} from 'use-immer'
import {initialTravelPlan} from './travel.ts'

interface PlaceTreeProps {
id: number
parentId: number
plan: TravelPlan
onComplete: (parentId: number, id: number) => void
}

interface TravelPlan {
[key: number]: {
id: number
title: string
childIds: number[]
}
}

export default function HookDemo() {
const [plan, setPlan] = useImmer(initialTravelPlan)
const root = plan[0]
const planetIds = root.childIds
const handleComplete = (parentId: number, id: number) => {
setPlan(draft => {
if (id===0) return
handleChildrenDelete(id)
handleParentDelete(parentId,id)

 function handleParentDelete(pId: number,cId: number) {
 const parent = draft[pId]
 if (!parent) return
 parent.childIds = parent.childIds.filter((childId) => childId !== cId)
 **// if the parent has no more children, delete it too**
 if (parent.childIds.length === 0 && pId !== 0) {
 const grandParentId = Object.values(draft).find(p => p.childIds.includes(pId))?.id
 if (grandParentId !== undefined) {
 handleParentDelete(grandParentId, pId)
 }
 delete draft[pId]
 }
 }
 function handleChildrenDelete(childId: number) {
 const child = draft[childId]
 if (!child) return
 child.childIds.forEach((grandChildId) => {
 handleChildrenDelete(grandChildId)
 })
 delete draft[childId]
 }
 })
 console.log(parentId, id)
}
return (
 <div>
 <h2>Place to Visit</h2>
 <ol>
 {planetIds.map((id) => (
 <PlaceTree
 id={id}
 key={id}
 parentId={0}
 plan={plan}
 onComplete={handleComplete}
 />
 ))}
 </ol>
 </div>
)

}

function PlaceTree({id, parentId, plan, onComplete}: PlaceTreeProps) {
const place = plan[id]
const childIds = place.childIds
return (