Javascript 应用程序找不到父级时崩溃

有一个包含值的表：

  comment_id |  user_Id  | product_id | parent_id | reply_id | ... |
--------------------------------------------------------------------
    164      |     7     |      40     |   null   |   null   | ... |
    165      |     7     |      40     |   164    |   164    | ... |        
    166      |     7     |      40     |   164    |   164    | ... | 
    167      |     20    |      40     |   164    |   164    | ... |        
    168      |     20    |      40     |   164    |   164    | ... |        
    169      |     20    |      40     |   164    |   164    | ... |    
    170      |     7     |      40     |   180    |   180    | ... |       

我定义要处理子注释的父级：

    let comments = data_comments.rows;
    let comments_array = [];
    let tmp = {};
    for (let c of comments) {
        if (c.parent_id === null) {              
            comments_array.push(c);
            tmp[c.comment_id] = c;
            tmp[c.comment_id].nested_comments = [];
        } else {
            tmp[c.parent_id].nested_comments = tmp[c.parent_id].nested_comments || [];
            tmp[c.parent_id].nested_comments.push(c);
        }
    }

但我的问题是，当父级未发现应用程序因错误而失败时：

TypeError: Cannot read property 'nested_comments' of undefined

这里170条注释没有这样的父项，因此应用程序失败

如何确保在辅助注释中没有指定父项时，应用程序不会失败

然后我删除了注释170，因为应用程序随之下降 我传递给客户机的格式：

"productDetails": {
        "product_id": 40,
        "product_name": "slippers",
        "product_description": "this slippers is good",
        "original_price": 7600,
        "sale_price": 4500,
        "discount": 41,
        "creating_date": "2019-02-28T04:43:04.000Z",
        "end_date": "2019-03-12T07:02:19.000Z",
        "date_period": "Mar 7 - Mar 12",
        "product_photos": [
            "https://..."
        ],
        "quantity_available": 150,
        "store_id": 9,
        "store_name": "Name Store",
        "contact_number": "123",
        "type_location": "SITY",
        "categorie": "LAPTOPS COMPUTERS",
        "starting_date": "2019-03-07T07:02:19.000Z",
        "likes": "0",
        "bookmarks": false,
        "is_liked": false,
        "comments": [
            {
                "comment_id": 164,
                "user_id": 7,
                "product_id": 40,
                "parent_id": null,
                "reply_id": null,
                "user_name": "Name Parent",
                "user_avatar": "https://...,
                "user_comment": "like product",
                "date_comment": 1551693424,
                "nested_comments": [
                    {
                        "comment_id": 169,
                        "user_id": 20,
                        "product_id": 40,
                        "parent_id": "164",
                        "reply_id": "164",
                        "user_name": "Name",
                        "user_avatar": "https://...",
                        "user_comment": "like product",
                        "date_comment": 1551693567
                    },
                    {
                        "comment_id": 168,
                        "user_id": 20,
                        "product_id": 40,
                        "parent_id": "164",
                        "reply_id": "164",
                        "user_name": "Name",
                        "user_avatar": "https://...",
                        "user_comment": "like product",
                        "date_comment": 1551693559
                    },
                    {
                        "comment_id": 167,
                        "user_id": 20,
                        "product_id": 40,
                        "parent_id": "164",
                        "reply_id": "164",
                        "user_name": "Name",
                        "user_avatar": "https://...",
                        "user_comment": "like product",
                        "date_comment": 1551693542
                    },
                    {
                        "comment_id": 166,
                        "user_id": 7,
                        "product_id": 40,
                        "parent_id": "164",
                        "reply_id": "164",
                        "user_name": "Name",
                        "user_avatar": "https://...",
                        "user_comment": "like product",
                        "date_comment": 1551693480
                    },
                    {
                        "comment_id": 165,
                        "user_id": 7,
                        "product_id": 40,
                        "parent_id": "164",
                        "reply_id": "164",
                        "user_name": "Name",
                        "user_avatar": "https://...",
                        "user_comment": "like product",
                        "date_comment": 1551693457
                    }
                ],
                "is_last_page": true
            }
        ]
    }

---

正如我在问题注释中所述，您正在尝试访问未定义变量的属性。您可以通过使用两个循环来解决这个问题，这两个循环将正确地填充

注释\u数组

试试这个（未经测试）：

---

嵌套注释是注释的一部分吗？不，在这个字段中，我写下子注释并以JSONY格式传递。您的代码似乎认为

c.comment\u id

和

c.parent\u id

在某种程度上是匹配的，但我认为它们不匹配。请详细说明，您能否共享添加的格式。如果没有错误消息，我应该如何帮助您？错误与

TypeError相同：无法读取未定义的属性“嵌套注释”

您可以将

数据注释的内容粘贴到中吗？然后我可以重新创建一个工作示例。我按照您的要求做了，在izi comment 492的示例中，整个应用程序崩溃了
let comments = data_comments.rows;
let comments_array = [];
let tmp = {};

for (let c of comments) {
  tmp[c.comment_id] = c;
  c['nested_comments'] = [];
}

for (let c of comments) {
  if (c.parent_id !== null && tmp[c.parent_id] !== undefined) {
    tmp[c.parent_id]['nested_comments'].push(c);
  } else {
    comments_array.push(c);
  }
}