树形 多层嵌套 取出每层的id 放在一个数组中

let data = [
    {
      firstLetter: 'A',
      fullName: '安徽省安庆市大观区',
      id: 1,
      childrens: [
        {
          firstLetter: 'B',
          fullName: '安徽',
          id: 2,
          childrens: [
            { firstLetter: 'D', fullName: '安徽', id: 3 },
            {
              firstLetter: 'E', fullName: '安徽',  id: 4,
            },
          ],
        },
        {
          firstLetter: 'C',
          fullName: '安徽',
          id: 5,
          childrens: [
            { firstLetter: 'F', fullName: '安徽', id: 6 },
            { firstLetter: 'G', fullName: '安徽', id: 7 },
　　　　　　　{ firstLetter: 'H', fullName: '安徽', id: 8 }
          ],
        },
      ],
    },
];
let arr = [];
function getIdFn(data){
    data.forEach(item=>{
        arr.push(item.id)
        if(item.hasOwnProperty("childrens")){
            getIdFn(item.childrens)
        }
    })
    return arr
}
let res = getIdFn(data)
console.log('%c 🥩 res: ', 'font-size:20px;background-color: #7F2B82;color:#fff;', res)

　　//[1,2,3,4,5,6,7,8]