🐶

      function find(array, param, paramKey = "id", childrenKey = "children") {
      let res
      for (let index = 0; index < array.length; index++) {
        function fn() {
          if (array[index][paramKey] === param) return array[index]
          if (array[index][childrenKey] && array[index][childrenKey].length)
            return find(array[index][childrenKey], param)
        }
        if (fn()) {
          res = fn()
          break
        }
      }
      return res
    }
    const arr = [{
        "id": 1,
        "children": [{
            "id": 2,
          },
          {
            "id": 3,
            "children": [{
              "id": 4,
            }]
          }
        ]
      },
      {
        "id": 5,
        "children": [{
          "id": 6,
        }]
      }
    ]
    console.log(find(arr, 1))
    console.log(find(arr, 999))
    console.log(find(arr, 6))