you need to get a collection of all the id of isCheck = true

list: [{
  id: "1",
  isCheck: false,
  children: [{
    id: "1-1",
    isCheck: false,
    children: null
  }, {
    id: "1-2",
    isCheck: true,
    children: null
  }]
}, {
  id: "2",
  isCheck: false,
  children: [{
    id: "2-1",
    isCheck: true,
    children: null
  }]
}, {
  id: "3",
  isCheck: true,
  children: null
}]

think of using recursive algorithm to flatten and degrade the array, but the data obtained is not right. I hope to get the data

["1-2", "2-1", "3"]

  steamroller: function (arr) {
    let newArr = []
    let flat = function (item) {
      for (var i = 0; i < item.length; iPP) {
        if (Array.isArray(item[i].children)) {
          flat(item[i])
        } else {
          newArr.push(item[i])
        }
      }
    }
    flat(arr)
    return newArr
  }

ask for help!