javascript - 使用lodash创建多级查找表

Question

假设一个 api 正在返回 apiResult 中的结构，我想创建一个两级索引来查找给定作者对给定文章的评论。

作者、文章和评论的查找表本身很简单，但我在 CommentsByArticleAndAuthor 查找表上遇到了困难。

在 mapped 结构中，我展示了我如何为三个“简单”部分制作查找索引，以及我如何希望 CommentsByArticleAndAuthor看。

我怎样才能继续生成这个索引？

var apiResult = {
  Authors: [
    {
      Id: "author-id-1",
      Name: "Author One"
    },
    {
      Id: "author-id-2",
      Name: "Author Two"
    }
  ],
  Articles: [
    {
      Id: "article-id-1",
      Title: "This Great Article"
    }
  ],
  Comments: [
    {
       Id: "comment-id-1",
       AuthorId: "author-id-1",
       ArticleId: "article-id-1",
       Comment: "that great, hu?" 
    },
    {
      Id: "comment-id-2",
      AuthorId: "author-id-2",
      ArticleId: "article-id-1",
      Comment: "yes, that great"
    }
  ]
}

var mapped = {
  Authors: _.keyBy(apiResult.Authors, 'Id'),
  Articles: _.keyBy(apiResult.Articles, 'Id'),
  Comments: _.keyBy(apiResult.Comments, 'Id'),
  CommentsByArticleAndAuthor: {
    "article-id-1": {
      "author-id-1": [ "comment-id-1" ],
      "author-id-2": [ "comment-id-2" ]
    }
  }
}

console.log(JSON.stringify(mapped, null, 2));

<script src="https://cdn.jsdelivr.net/lodash/4.17.4/lodash.min.js"></script>

Answer 1

您可以迭代评论并构建分层对象结构。

var apiResult = { Authors: [{ Id: "author-id-1", Name: "Author One" }, { Id: "author-id-2", Name: "Author Two" }], Articles: [{ Id: "article-id-1", Title: "This Great Article" }], Comments: [{ Id: "comment-id-1", AuthorId: "author-id-1", ArticleId: "article-id-1", Comment: "that great, hu?" }, { Id: "comment-id-2", AuthorId: "author-id-2", ArticleId: "article-id-1", Comment: "yes, that great" }] },
    mapped = { CommentsByArticleAndAuthor: {} };

apiResult.Comments.forEach(function (o) {
    var ref = mapped.CommentsByArticleAndAuthor;

    ref[o.ArticleId] = ref[o.ArticleId] || {};
    ref[o.ArticleId][o.AuthorId] = ref[o.ArticleId][o.AuthorId] || [];
    ref[o.ArticleId][o.AuthorId].push(o.Id);
});

console.log(mapped);

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对于更动态的方法，您可以为层次结构使用数组，为默认值使用对象。

var apiResult = { Authors: [{ Id: "author-id-1", Name: "Author One" }, { Id: "author-id-2", Name: "Author Two" }], Articles: [{ Id: "article-id-1", Title: "This Great Article" }], Comments: [{ Id: "comment-id-1", AuthorId: "author-id-1", ArticleId: "article-id-1", Comment: "that great, hu?" }, { Id: "comment-id-2", AuthorId: "author-id-2", ArticleId: "article-id-1", Comment: "yes, that great" }] },
    mapped = { CommentsByArticleAndAuthor: {} };

apiResult.Comments.forEach(function (o) {
    ['ArticleId', 'AuthorId'].reduce(function (r, k) {
        return r[o[k]] = r[o[k]] || { AuthorId: [] }[k] || {};
    }, mapped.CommentsByArticleAndAuthor).push(o.Id);
});

console.log(mapped);

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