unescape unicode and utf-8 hex chars

unescapeUnicode.ts

/**
 *   \xe2\x98\x89 Mercury  -> ☉ Mercury
 **/
function unescapeUtf8Hex(s: string): string {
   if (typeof s !== 'string') return s;
   return s.replace(/(?:\\x[\da-fA-F]{2})+/g, (m) => decodeURIComponent(m.replace(/\\x/g, '%')));
}

/**
 *    \\\\U0001F528 hello \\U0001F528 hello -> 🔨 hello 🔨 hello
 **/
function unescapeUnicode(s: string): string {
   if (typeof s !== 'string') return s;
   return s.replace(/\\\\u[0-9A-Fa-f]*|\\u[0-9A-Fa-f]*/gi, (s) => {
      const escaped = s.replace(/\\\\u/i, '\\u');
      const codePoint = escaped.replace(/\\u/i, '0x');
      try {
         return String.fromCodePoint(Number(codePoint));
      } catch (e) {
         return s;
      }
   });
}

export function unescapeAll(s: string): string {
   return unescapeUnicode(unescapeUtf8Hex(s));
}

describe('unescapeUnicode', () => {
   test('should handle doubled escaped and escaped unicode code points', () => {
      const s = '\\\\U0001F528 hello \\U0001F528 hello - \\xe2\\x98\\x89 Mercury';

      expect(unescapeAll(s)).toBe('🔨 hello 🔨 hello - ☉ Mercury');
   });

   test('should handle invalid escaped and escaped unicode code points', () => {
      const s = '\\\\Ue201F528 hello \\Ue201F528 hello';

      expect(unescapeAll(s)).toBe(s);
   });

   test('should handle invalid strings', () => {
      // @ts-ignore
      expect(unescapeAll(2)).toBe(2);
   });
});