Fast URL.parse() polyfill

url-parse-polyfill.ts

/**
 * Fast URL.parse() polyfill
 *
 * Copyright (c) 2024 Transcend Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
export default URL.parse ||= (() => {
  const call = Function.prototype.call.bind(Function.prototype.call);
  const { document, URLPattern, HTMLInputElement, ValidityState } = self;
  const testURLPattern = URLPattern?.prototype?.test;
  const anyValidURLPattern = URLPattern && new URLPattern();
  const HTML_NS = 'http://www.w3.org/1999/xhtml';

  const validateURL =
    URLPattern &&
    ((input: unknown): boolean =>
      input !== null &&
      call(testURLPattern, anyValidURLPattern, `${input}`, 'http://-'));

  /**
   * Parse URL input into a URL instance and throws an error if the
   * input is invalid.
   *
   * @param input - Stringifiable URL input (e.g. a string or URL instance)
   * @param context - Context URL
   * @returns Parsed URL
   */
  const parseURL = (input: string | URL, context?: string | URL): URL =>
    new URL(input, context);

  /**
   * Parses and validates any URL string. Returns null if the URL is invalid.
   *
   * @param input - Stringifiable URL input (e.g. a string or URL instance)
   * @param context - Context URL
   * @returns Parsed URL or null
   */
  const parseAndValidateURL = (
    input: string | URL,
    context?: string | URL,
  ): URL | null => {
    try {
      return parseURL(input, context);
    } catch (ex) {
      return null;
    }
  };

  /**
   * Parses stringifiable URL input into a URL instance and
   * returns null if the input is invalid.
   *
   * Implemented with three tiers:
   * 1. fastest: URLPattern validation + new URL()
   * 2. fast for absolute URLs: DOM validation + new URL() for absolute URLs / try...catch new URL() for relative URLs
   * 3. slowest: try...catch new URL()
   *
   * @param input - Stringifiable URL input (e.g. a string or URL instance)
   * @param context - Context URL
   * @returns Parsed URL or null
   */
  const parsePotentialURL: (
    input: string | URL,
    context?: string | URL,
  ) => URL | null = validateURL
    ? // URLPattern validator can be used instead of try...catch
      (input, context) => (validateURL(input) ? parseURL(input, context) : null)
    : document
      ? // if DOM is available, use input[type=url] validation for absolute URLs
        (() => {
          const validator = document.createElementNS(
            HTML_NS,
            'input',
          ) as HTMLInputElement;
          validator.type = 'url';
          const validityState = validator.validity;
          const setValue = Object.getOwnPropertyDescriptor(
            HTMLInputElement.prototype,
            'value',
          )!.set;
          const getValidity = Object.getOwnPropertyDescriptor(
            ValidityState.prototype,
            'valid',
          )!.get;
          return (input, context) => {
            // DOM can only validate absolute urls, so we still have to fallback
            // to parseAndValidateURL for everything that doesn't pass this check
            call(setValue, validator, input);
            return input && call(getValidity, validityState)
              ? parseURL(input, context)
              : parseAndValidateURL(input, context);
          };
        })()
      : parseAndValidateURL;

  return parsePotentialURL;
})();