handrolled rowset to JSON conversion

handrolled.js

const handrolled = (rs) => {
    const authors = {}

    rs.forEach(r => {
        const authname = [r.last_name, r.first_name].join(',');
        if (!authors[authname]) {
            authors[authname] = {
                categories: {}
            }
        }
        var author = authors[authname];
        if (!author.categories[r.category]) {
            author.categories[r.category] = {
                titles: []
            }
        }
        var category = author.categories[r.category]
        if (!category.titles.includes(r.title)) {
            category.titles.push(r.title)
        }
    })

    return authors;
}