Sorting a list of items into different categories - mongodb

Question

Imagine a site that lists different articles with different subjects, and you as a user can mark your favorite articles to read later. Favorited articles get saved and displayed in your personal little space on this site like this:
Movies
Upcoming summer blockbusters
Will there never be a end of Superheroes?
Are romcoms dead?
Science
Bezos or Musk, who will reach Mars first?
Philosophy
How can mirrors be real if our eyes aren't real?
Etc, etc.
I have saved each article in the database with the following fields:
{
articleName: "Upcoming summer blockbusters",
subject: "Movies",
link: //link to the article
}
Then when a user favorites one I simply duplicate it into his own collection in the database.
Then comes the problems...
I could iterate through his articles and print them out on his user page like so:
<ul>
{{#each articles}}
<heading>{{subject}}</heading> //how do I avoid duplicates?
<li>{{articleName}}</li>
{{/each}}
</ul>
This, however, would duplicate the subjects that are shared across multiple articles.
I could iterate through the subjects only (making them into an array that checks for duplicates, for instance) and print them out:
<ul>
{{#each subjects}}
<heading>{{this}}</heading>
<li>{{../articleName}}</li> //how do I print the correct one?
{{/each}}
</ul>
But this way would be completely broken, since the articles wouldn't show up under the correct subject headings...
How should I proceed?

Answer 1

Actually I think you should store favorite articles only, the way you did. It will be way simpler to handle cases like article deletions. Just parse the articles in a helper function, and you should get the same result:
favArticlesBySubjects: function () {
var favArticles = Meteor.user().profile.favArticles;
var articlesBySubject = [];
favArticles.forEach(function (article) {
var index = _.findIndex(articlesBySubject, function (obj) {
return obj.subject === article.subject;
});
if (index < 0)
articlesBySubject.push({subject: article.subject, articles:[article]});
else
articlesBySubject[index].articles.push(article);
};
return articlesBySubject;
}
This way, you can display your favorite articles using :
{{#each favArticlesBySubjects}}
<heading>{{subject}}</heading>
<ul>
{{#each articles}}
<li>{{articleName}}</li>
{{/each}}
</ul>
{{/each}}