TypeScript version of rotUrl

roturl.ts

// From https://github.com/locutusjs/locutus/blob/main/src/php/strings/strtr.js
// but adapted to the all-strings case.
function strtr(str: string, trFrom: string, trTo: string) {
  let j = 0;
  let lenStr = 0;
  let lenFrom = 0;
  let istr = '';
  let ret = '';
  let match = false;

  // Walk through subject and replace chars when needed
  lenStr = str.length;
  lenFrom = trFrom.length;

  for (let i = 0; i < lenStr; i += 1) {
    match = false;
    istr = str.charAt(i);
    for (j = 0; j < lenFrom; j += 1) {
      if (istr === trFrom.charAt(j)) {
        match = true;
        break;
      }
    }
    if (match) {
      ret += trTo.charAt(j);
    } else {
      ret += str.charAt(i);
    }
  }

  return ret;
}

/**
 * Rot35 for URLs. To avoid increasing size during urlencode(), commonly encoded
 * chars are mapped to more rarely used chars (end of the uppercase alpha).
 * PHP version: https://gist.github.com/mrclay/1225832
 */
export default function rotUrl(url: string) {
  return strtr(
    url,
    './-:?=&%# ZQXJKVWPY abcdefghijklmnopqrstuvwxyz123456789ABCDEFGHILMNORSTU',
    'ZQXJKVWPY ./-:?=&%# 123456789ABCDEFGHILMNORSTUabcdefghijklmnopqrstuvwxyz',
  );
}