Vulcan/packages/nova-categories/lib/parameters.js

import Categories from "./collection.js";
import { addCallback } from 'meteor/nova:core';

// Category Default Sorting by Ascending order (1, 2, 3..)
const CategoriesAscOrderSorting = (parameters, terms) => {
  parameters.options.sort = {order: 1};
  
  return parameters;
};

addCallback('categories.parameters', CategoriesAscOrderSorting);

// Category Posts Parameters
// Add a "categories" property to terms which can be used to filter *all* existing Posts views. 
const PostsCategoryParameter = (parameters, terms) => {

  const cat = terms.cat || terms["cat[]"];

  // filter by category if category slugs are provided
  if (cat) {

    let categoriesIds = [];
    let selector = {};

    if (typeof cat === "string") { // cat is a string
      selector = {slug: cat};
    } else if (Array.isArray(cat)) { // cat is an array
      selector = {slug: {$in: cat}};
    }

    // get all categories passed in terms
    let categories = Categories.find(selector).fetch();
    
    // for each category, add its ID and the IDs of its children to categoriesId array
    categories.forEach(function (category) {
      categoriesIds.push(category._id);
      categoriesIds = categoriesIds.concat(_.pluck(Categories.getChildren(category), "_id"));
    });

    parameters.selector.categories = {$in: categoriesIds};
  }
  
  return parameters;
}

addCallback("posts.parameters", PostsCategoryParameter);