function readProductFilters(locationHref = window.location.href) {
  const url = new URL(locationHref);
  const params = url.searchParams;

  return {
    category: params.get("category") ?? "all",
    page: Number(params.get("page") ?? "1"),
    tags: params.getAll("tag"),
    preview: params.has("preview"),
  };
}

const filtersWithQuery = readProductFilters(
  "https://www.example.com/products?category=books&page=2&tag=javascript&tag=web&preview",
);
const filtersWithoutQuery = readProductFilters("https://www.example.com/products");

console.log("with query:");
console.log(JSON.stringify(filtersWithQuery, null, 2));
console.log("without query:");
console.log(JSON.stringify(filtersWithoutQuery, null, 2));