rickvanlieshout.com/src/hooks/use-categories-list.ts

import { graphql, useStaticQuery } from "gatsby";

interface CategoriesQueryResult {
  allMarkdownRemark: {
    group: Array<{
      fieldValue: string;
      totalCount: number;
    }>;
  };
}

const useCategoriesList = () => {
  const { allMarkdownRemark } = useStaticQuery<CategoriesQueryResult>(
    graphql`
      query CategoriesListQuery {
        allMarkdownRemark(
          filter: { frontmatter: { template: { eq: "post" }, draft: { ne: true } } }
        ) {
          group(field: { frontmatter: { category: SELECT } }) {
            fieldValue
            totalCount
          }
        }
      }
    `
  );

  return allMarkdownRemark.group ?? [];
};

export default useCategoriesList;