[Suggestion]: Improvements to an example in the document

從選擇狀態結構頁面上的範例開始，將其目前的刪除行為與提供的 HookDemo 和 PlaceTree 程式碼進行比較。更新文件範例，使刪除唯一的子項也會移除現在為空的祖先，然後驗證範例中呈現的樹狀結構和刪除行為。

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 (