Untitled

const finalList = products
  .filter(el => 
    (el.name.toLowerCase().includes(filterText.toLowerCase()) &&
    (!inStockOnly || (inStockOnly && el.stocked)))
  )
  .reduce((acc, curr) => {
    if (curr.category !== acc.lastCategory) {
      acc.output.push(<ProductCategoryRow key={curr.category} category={curr.category} />);
      acc.lastCategory = curr.category;
    }
    acc.output.push(<ProductRow key={curr.name} product={curr} />);
    return acc;
  }, { lastCategory: null, output: [] });