Answer 1

const arr = [
    {
        id: 1,
        name: '广东',
        children: [
            {
                id: 11,
                name: '深圳',
                children: [
                    {
                        id: 111,
                        name: '南山区'
                    },
                    {
                        id: 112,
                        name: '福田区'
                    }
                ]
            }
        ]
    }
]

const id = 112

const fn = (treeData, idsList = [], ids = []) => {
    treeData.forEach(item => {
        const { id, children } = item
        const tempIds = [].concat(ids)
        tempIds.push(id)

        idsList.push(tempIds);

        if (children && !!children.length) {
            fn(children, idsList, tempIds);
        }
    });

    return idsList;
};

const list = fn(arr)


const result = list.filter(item => {
    const lastValue = item[item.length - 1]

    return Number(lastValue) === Number(id)
})

思路：
1、将数组转换为多个一维数组，结果如下所示：

2、循环第一步所得的结果，判断最后一位是不是和要查询的id相同，如果是那么就返回结果

Answer 2

https://www.jianshu.com/p/54cc04190252
浏览器的缓存机制

这篇完美~