題目：實現一個對樹型結構進行過濾的函數，其中樹形結構的格式

題目：實現一個對樹型結構進行過濾的函數，其中樹形結構的格式如下： tree = [ {name: ‘A’}, {name: ‘B’,
children: [ {name: ‘A’}, {name: ‘AA’, children: […]} ]}, {name: ‘C’}
]

1. 假設我輸入的 str 爲 A 則過濾後返回的結果爲 [ {name: ‘A’}, {name: ‘B’, children: [ {name: ‘A’} ]} ]

2. 假設我輸入的 str 爲 AA 則過濾後返回的結果爲 [ {name: ‘B’, children: [ {name: ‘AA’, children: […]} ]} ]

3. 假設我輸入的 str 爲 B 則過濾後返回的結果爲 [ {name: ‘B’, children: [ {name: ‘A’}, {name: ‘AA’, children: […]} ]} ]
   // 實現該函數，要求不允許對原有的tree做任何修改，最終返回結果是一棵新結構出來的樹 function filter (tree, str) {

   }

const tree = [
  { name: "A" },
  { name: "B", children: [{ name: "A" }] },
  {
    name: "AA",
    children: [
      { name: "BB" },
      { name: "C" },
      { name: "D", children: [{ name: "A" }] },
      { name: "A" },
    ],
  },
  { name: "D", children: [{ name: "C", children: [{ name: "AA" }] }] },
];
function clear(tree, str) {
  if (!tree) return [];//處理葉節點
  let result = [];
  
  tree.map((item) => {
    let it = { ...item }; //每項淺拷貝一下保證不影響原來的tree
    if (it.name === str) {
      result.push(it);
    } else {
      let obj = clear(it.children, str);
      //得到children的返回的result數組，放到拷貝對象的children中
      if (obj.length > 0) {
        it.children = obj;
        result.push(it);
      }
    }
  });
  return result;//每層返回一個數組
}
console.log(clear(tree, "A"));
console.log(tree);