过滤器中的过滤器在一种情况下有效，而在另一种情况下无效

Question

所以我碰巧浏览了这两个帖子：

1. ES6 .filter within a .filter

   [ { "id": 0, "title": "happy dayys", "owner": {"id": "1", "username": "dillonraphael"}, "tags": [{"value": "Art", "label": "Art"}], "items": [] }, { "id": 1, "title": "happy dayys", "owner": {"id": "1", "username": "dillonraphael"}, "tags": [{"value": "Architecture", "label": "Architecture"}], "items": [] }, ]

在此 OP 中，尝试通过无效的嵌套过滤器过滤数据：

const tagMoodboards = _moodboards.filter(mb => { return mb.tags.filter(t => t.value == name) });

原因是内部 filter 返回一个数组（真实），所以对于外部数组，它变成这样 _moodboards.filter(mb => true) 因此它打印整个数组

然后有类似的问题

1. How to filter nested array in javascript

哪里有这样的数据：

{
  "list": [
    {
      "deviceId": "2a-d539-4031-9bfc-4a42f2f765cf",
      "versions": [
        {
          "id": "764c20-a213-9235f4b553b3",
          "createdTime": 1590361208034,
          "files": [
            {
              "fileType": "VLAN"
            },
            {
              "fileType": "STARTUPCONFIG",
            }
          ],
          "startupRunningStatus": "OUT_OF_SYNC",
          "createdBy": "SCHEDULED"
        },
        {
          "id": "9bd33-a45a-ed2fefc46931",
          "createdTime": 1589972337717,
          "files": [
            {
              "fileType": "VLAN",
            },
            {
              "fileType": "STARTUPCONFIG",
            },
            {
              "fileType": "RUNNINGCONFIG",
            }
          ],
          "startupRunningStatus": "IN_SYNC",
          "createdBy": "SCHEDULED_FIRST_TIME"
        }
      ]
    }
  ]
}

并且 OP 想要过滤数据，它应该只返回存在“fileType”：“RUNNINGCONFIG”和“fileType”：“STARTUPCONFIG”的数组

但在这种情况下，filter 中的 filter 似乎可以完成这项工作

let versionsData = obj.list[0].versions; versionsData = versionsData.filter( versions => { return versions.files.filter( m => { return m.fileType === "RUNNINGCONFIG" || m.fileType === "STARTUPCONFIG" }).length > 1 } ); console.log(versionsData);

在第二种情况下，我觉得它应该遵循相同的模式 versionData = versionData.filter(versions => true) 因此返回完整的数组。

那么，我的问题是我到底错过了什么？我哪里错了？

Answer 1

您必须将其更改为：

const tagMoodboards = _moodboards.filter(mb => { return mb.tags.filter(t => t.value == name).length });

对于拉胡尔： 将此代码粘贴到浏览器控制台中：

let arr = [
    {
    "id": 0,
    "title": "happy dayys",
    "owner": {"id": "1", "username": "dillonraphael"},
    "tags": [{"value": "Art", "label": "Art"}],
    "items": []
    },
    {
    "id": 1,
    "title": "happy dayys",
    "owner": {"id": "1", "username": "dillonraphael"},
    "tags": [{"value": "Architecture", "label": "Architecture"}],
    "items": []
    },
];

console.info(arr.filter(mb => { return mb.tags.filter(t => t.value == 'Art') })); // -> 2 hits (=wrong)
console.info(arr.filter(mb => { return mb.tags.filter(t => t.value == 'Art').length })); // -> 1 hit (=right)