为了得到未定义的内部

Question

我有这个JSON数据：

var lists = [{
        "listId": 1,
        "permission": "WRITE"
    }, {
        "listId": 2,
        "permission": "WRITE"
    }, {
        "listId": 2,
        "permission": "READ"
    }, {
        "listId": 3,
        "permission": "READ"
    }, {
        "listId": 3,
        "permission": "WRITE"
    }, {
        "listId": 5,
        "permission": "WRITE"
    }]

而这个：

var arr = [{
    "listId": 1,
    "confidentiality": "PUBLIC",
    "listName": "List name here..1",
    "permission": "WRITE"
}, {
    "listId": 2,
    "confidentiality": "PUBLIC",
    "listName": "List name here..2",
    "permission": "READ"
}, {
    "listId": 3,
    "confidentiality": "CONFIDENTIAL",
    "listName": "List name here..3",
    "permission": "WRITE"
}, {
    "listId": 4,
    "confidentiality": "CONFIDENTIAL",
    "listName": "List name here..4",
    "permission": "WRITE"
}, {
    "listId": 5,
    "confidentiality": "CONFIDENTIAL",
    "listName": "List name here..5",
    "permission": "WRITE"
}]

使用这个for和nested，我必须过滤来自arr的数据，并将其推送到results[]，如果在列表中匹配listId和权限.E 211

var result = [];

for(var i = 0; i < arr.length; i++) {   
  for(var j = 0; j < lists.length; j++) {     
     if( (arr[j].listId == lists[i].listId) && (arr[j].permission == lists[i].permission) ) {
        result.push(arr[j]);
     }
  }
}
console.log(result);

问题是，如果listId小于lists.length，则得到未定义的arr.length

知道我怎么解决这个问题吗？

Answer 1

问题是，如果listId小于lists.length，则得到未定义的arr.length

您需要为它们自己的数组使用各自的索引，即i用于arr，j用于lists

if( (arr[i].listId == lists[j].listId) && (arr[i].permission == lists[j].permission) )

Answer 2

您可以通过查找权限表稍微更改一下结构，并且只对结果集使用一个循环。

​

var lists = [{ listId: 1, permission: "WRITE" }, { listId: 2, permission: "WRITE" }, { listId: 2, permission: "READ" }, { listId: 3, permission: "READ" }, { listId: 3, permission: "WRITE" }, { listId: 5, permission: "WRITE" }],
    array = [{ listId: 1, confidentiality: "PUBLIC", listName: "List name here..1", permission: "WRITE" }, { listId: 2, confidentiality: "PUBLIC", listName: "List name here..2", permission: "READ" }, { listId: 3, confidentiality: "CONFIDENTIAL", listName: "List name here..3", permission: "WRITE" }, { listId: 4, confidentiality: "CONFIDENTIAL", listName: "List name here..4", permission: "WRITE" }, { listId: 5, confidentiality: "CONFIDENTIAL", listName: "List name here..5", permission: "WRITE" }],
    permissions = {},
    result;

lists.forEach(function (p) {
    permissions[p.listId] = permissions[p.listId] || {};
    permissions[p.listId][p.permission] = true;
});

result = array.filter(function (a) {
    return permissions[a.listId] && permissions[a.listId][a.permission];
});

console.log(result);

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