Function normalizeUrl

packages/docusaurus-utils/src/urlUtils.ts:22–106

(rawUrls: string[])

 * @throws {TypeError} If any of the URL segment is not a string, this throws.
 */
export function normalizeUrl(rawUrls: string[]): string {
  const urls = [...rawUrls];
  const resultArray = [];

  let hasStartingSlash = false;
  let hasEndingSlash = false;

  const isNonEmptyArray = (arr: string[]): arr is [string, ...string[]] =>
    arr.length > 0;

  if (!isNonEmptyArray(urls)) {
    return '';
  }

  // If the first part is a plain protocol, we combine it with the next part.
  if (urls[0].match(/^[^/:]+:\/*$/) && urls.length > 1) {
    const first = urls.shift()!;
    if (first.startsWith('file:') && urls[0].startsWith('/')) {
      // Force a double slash here, else we lose the information that the next
      // segment is an absolute path
      urls[0] = `${first}//${urls[0]}`;
    } else {
      urls[0] = first + urls[0];
    }
  }

  // There must be two or three slashes in the file protocol,
  // two slashes in anything else.
  const replacement = urls[0].match(/^file:\/\/\//) ? '$1:///' : '$1://';
  urls[0] = urls[0].replace(/^(?<protocol>[^/:]+):\/*/, replacement);

  for (let i = 0; i < urls.length; i += 1) {
    let component = urls[i];

    if (typeof component !== 'string') {
      throw new TypeError(`Url must be a string. Received ${typeof component}`);
    }

    if (component === '') {
      if (i === urls.length - 1 && hasEndingSlash) {
        resultArray.push('/');
      }
      continue;
    }

    if (component !== '/') {
      if (i > 0) {
        // Removing the starting slashes for each component but the first.
        component = component.replace(
          /^\/+/,
          // Special case where the first element of rawUrls is empty
          // ["", "/hello"] => /hello
          component.startsWith('/') && !hasStartingSlash ? '/' : '',
        );
      }

      hasEndingSlash = component.endsWith('/');
      // Removing the ending slashes for each component but the last. For the