javascript - 合并多对一的对象列表

Question

我当前有两个数据库表，代表多对一关系。事件，具有 ID(整数、自动增量、主键)和名称(varchar(255)，不为 null)；和 ActivitySlugs，它有一个 ID(与上面相同)、一个 slugname(非 null varchar)和一个 Activity_id(Activities.id 的外键)。

目前，我应该获得所有事件及其所有 slugs 的列表(作为一个列表)，因此它看起来像这样:

[
    {id: 1, name: "long name", slugs: ["nick", "names"]},
    {id: 2, name: "foobar", slugs: ["foo", "bar"]}
]

天真的解决方案(也是我能想到的唯一一个)是在每个表上执行“SELECT *”，然后合并它们，但随后我得到的数据如下所示:

activities = [
    {id: 1, name: "long name"},
    {id: 2, name: "foobar"}
]
slugs = [
    {id: 1, slugname: "nick", activity_id: 1},
    {id: 2, slugname: "names", activity_id: 1},
    {id: 3, slugname: "foo", activity_id: 2},
    {id: 4, slugname: "bar", activity_id: 2}
]

然后我可以迭代两者并添加它们:

activities.forEach(function(activity) {
    slugs = [];
    activitySlugs.forEach(function(slug) {
        if (slug.activity_id == activity.id) {
            slugs.push(slug.name);
        }
    });
    activity.slugs = slugs;
);

这感觉笨拙、缓慢且不精致。它肯定根本无法扩展。不幸的是，我似乎找不到更好的方法来让它们与这样的数组合并为多对一。

Answer 1

您可以构建一个 id2activity 映射来通过 ID 访问任何事件:

var id2activity = {};
activities.forEach(function(activity) {
    activity.slugs = [];
    id2activity[activity.id] = activity;
);

activitySlugs.forEach(function(slug) {
    id2activity[slug.activity_id].slugs.push(slug.name);
});