javascript - 如何修复我的建筑树功能。如果 parent ID 不存在

Question

我正在设置构建树函数。一切正常，直到我添加一个 parentID 不存在的文档。根节点也应该是最小的 paarentID。即使 parentID 不是“0”。我不知道我做错了什么。

我试图在某处添加一个 if 子句，但没有成功。

function list_to_tree(list) {
          var map = {},
            node,
            roots = [],
            i;




          for (i = 0; i < list.length; i += 1) {

            map[list[i]._id] = i; // initialize the map

            list[i].children = []; // initialize the children
            list[i].link = []; // initialize the link field
          }



          for (i = 0; i < list.length; i += 1) {
            node = list[i];

            if (node._source.parentID !== '0') {

                    list[map[node._source.parentID]].children.push(node);

            } else {
              roots.push(node);
            }
          }
          return roots;


        }

        var entries = [

          {
            "_index": "fud_alvr",
            "_type": "analyse",
            "_id": "10",
            "_score": 1.4142135,
            "_source": {
              "ID": "10",
              "parentID": "0",
              "content": "Europa"
            }
          },
          {
            "_index": "fud_alvr",
            "_type": "analyse",
            "_id": "22",
            "_score": 1.4142135,
            "_source": {
              "ID": "22",
              "parentID": "10",
              "content": "Germany"
            }
          },
          {
            "_index": "fud_alvr",
            "_type": "analyse",
            "_id": "23",
            "_score": 1.4142135,
            "_source": {
              "ID": "23",
              "parentID": "90",
              "content": "Switzerland"
            }
          },
          {
            "_index": "fud_alvr",
            "_type": "analyse",
            "_id": "438",
            "_score": 1.4142135,
            "_source": {
              "ID": "438",
              "parentID": "22",
              "content": "München"
            }
          }

        ];
         console.log(list_to_tree(entries));

错误信息是:TypeError: 无法读取未定义的属性“children”

如果我删除瑞士，一切正常。

Answer 1

您可以检查父级是否存在，如果不存在，则将 '0' 指定为 parentID。

function list_to_tree(list) {
  var map = {},
    node,
    roots = [],
    i;

  for (i = 0; i < list.length; i += 1) {
    map[list[i]._id] = i; // initialize the map
    list[i].children = []; // initialize the children
    list[i].link = []; // initialize the link field
  }

  for (i = 0; i < list.length; i += 1) {
    node = list[i];

    // check if parent exists
    if (!(node._source.parentID in map)) node._source.parentID = '0';

    if (node._source.parentID !== '0') {
      list[map[node._source.parentID]].children.push(node);
    } else {
      roots.push(node);
    }
  }
  return roots;
}

var entries = [{ _index: "fud_alvr", _type: "analyse", _id: "10", _score: 1.4142135, _source: { ID: "10", parentID: "0", content: "Europa" } }, { _index: "fud_alvr", _type: "analyse", _id: "22", _score: 1.4142135, _source: { ID: "22", parentID: "10", content: "Germany" } }, { _index: "fud_alvr", _type: "analyse", _id: "23", _score: 1.4142135, _source: { ID: "23", parentID: "90", content: "Switzerland" } }, { _index: "fud_alvr", _type: "analyse", _id: "438", _score: 1.4142135, _source: { ID: "438", parentID: "22", content: "München" } }];

console.log(list_to_tree(entries));