按键分组对象数组 [英] Grouping an array of objects by key

问题描述

我有这个对象数组，我希望它们按它们的特定键分组，在这种情况下，是标签

I have this array of objects, and I want them to group by their specific key, in this case tags

var items = [
    {id: 0, tags: ["a"], name: "foo"},
    {id: 1, tags: [], name: "bar"},
    {id: 2, tags: ["a"], name: "bazz"},
    {id: 3, tags: ["b"], name: "wah"},
    {id: 4, tags: ["c"], name: "ikr"},
    {id: 5, tags: ["a"], name: "wtf"},
    {id: 6, tags: ["a","b"], name: "gtg"},
    {id: 7, tags: ["c"], name: "afk"}
]

所以我使用了下划线，就像这样：

And so I used underscore, like so:

var groupItems = _.groupBy(items, function(obj) {
  return obj.tags;
});

问题在于：

{
"a": [
        {"id": 0,"tags": ["a"],"name": "foo"},
        {"id": 2,"tags": ["a"],"name": "bazz"},
        {"id": 5,"tags": ["a"],"name": "wtf"}
     ],
"":  [
        {"id": 1,"tags": [],"name": "bar"}
     ],
"b": [
         {"id": 3,"tags": ["b"],"name": "wah"}
     ],
"c": [
         {"id": 4,"tags": ["c"],"name": "ikr"},
         {"id": 7,"tags": ["c"],"name": "afk"}
     ],
"a,b": [
         {"id": 6,"tags": ["a","b"],"name": "gtg"}
     ]

}

如果您还注意到，那些具有多个标签的人从数组<中创建了 joined 键。 code>标签，这是非常不理想的结果。如何将它们按标记分组并在它们具有多个标记

If you would also notice, those who has multiple tags, created a joined key from the array tags which is quite an undesirable result. How can I, group them by tags and duplicate the data when they have multiple tags

推荐答案

假定当项目具有多个标签 _。groupBy 时，您希望每个标签下都有重复的条目

Assuming you want duplicate entries under each tag when an item has multiple tags _.groupBy will not do what you want as it simply splits a collection up (won't duplicate entries).

相反，您将需要手动遍历项目，然后遍历每个项目的标签并为您建立列表（如果需要，可以使用 _。each ）：

Instead, you will need to loop over your items manually, then each item's tags and build up your list for you (you could use _.each if you wanted):

var items = [
    {id: 0, tags: ["a"], name: "foo"},
    {id: 1, tags: [], name: "bar"},
    {id: 2, tags: ["a"], name: "bazz"},
    {id: 3, tags: ["b"], name: "wah"},
    {id: 4, tags: ["c"], name: "ikr"},
    {id: 5, tags: ["a"], name: "wtf"},
    {id: 6, tags: ["a","b"], name: "gtg"},
    {id: 7, tags: ["c"], name: "afk"}
];

var groupItems = {};
for (var i = 0, item; item = items[i]; i++) {
  for (var t = 0, tag; tag = item.tags[t]; t++) {
    // If we do not have an array for our tag, add one
    groupItems[tag] = groupItems[tag] || [];
    // Push out item onto the tag's list in our groupItems
    groupItems[tag].push(item);
  }
}

哪个会给您：

{
  "a": [
    {"id": 0,"tags": ["a"],"name": "foo"},
    {"id": 2,"tags": ["a"],"name": "bazz"},
    {"id": 5,"tags": ["a"],"name": "wtf"},
    {"id": 6,"tags": ["a","b"],"name": "gtg"}
  ],
  "b": [
    {"id": 3,"tags": ["b"],"name": "wah"},
    {"id": 6,"tags": ["a","b"],"name": "gtg"}
  ],
  "c": [
    {"id": 4,"tags": ["c"],"name": "ikr"},
    {"id": 7,"tags": ["c"],"name": "afk"}
  ]
}

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