doc.silverstripe.org/src/utils/cleanHeaders.ts

/**
 * Removes the <em> tags caused by underscores in the {#id_with_underscores}
 * @param html
 */
const cleanHeaders = (html: string): string => {
    return html.replace(
        /<h([0-9])>(.*?)(\{#.*?<\/?em>.*?})/g,
        (_, level, title, tag) => `<h${level}>${title} ${tag.replace(/<\/?em>/g, '_')}`
    );
};

export default cleanHeaders;