docusaurus/packages/docusaurus-theme-classic/src/theme/TOC/index.tsx

/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import React from 'react';

import useTOCHighlight from '@theme/hooks/useTOCHighlight';
import type {TOCProps} from '@theme/TOC';
import styles from './styles.module.css';

const LINK_CLASS_NAME = 'table-of-contents__link';
const ACTIVE_LINK_CLASS_NAME = 'table-of-contents__link--active';
const TOP_OFFSET = 100;

/* eslint-disable jsx-a11y/control-has-associated-label */
function Headings({headings, isChild}: TOCProps & {isChild?: boolean}) {
  if (!headings.length) {
    return null;
  }
  return (
    <ul
      className={
        isChild ? '' : 'table-of-contents table-of-contents__left-border'
      }>
      {headings.map((heading) => (
        <li key={heading.id}>
          <a
            href={`#${heading.id}`}
            className={LINK_CLASS_NAME}
            // Developer provided the HTML, so assume it's safe.
            // eslint-disable-next-line react/no-danger
            dangerouslySetInnerHTML={{__html: heading.value}}
          />
          <Headings isChild headings={heading.children} />
        </li>
      ))}
    </ul>
  );
}

function TOC({headings}: TOCProps): JSX.Element {
  useTOCHighlight(LINK_CLASS_NAME, ACTIVE_LINK_CLASS_NAME, TOP_OFFSET);
  return (
    <div className={styles.tableOfContents}>
      <Headings headings={headings} />
    </div>
  );
}

export default TOC;