You shouldn't have to port anything. If you mean in the opposite case of two separate languages between client and server side then yeah, of course - by definition you're rewriting everything and there is no way to reuse code. I'm not clear how you're reaching anywhere near 50x complexity though. You're writing something like this on the client side (please excuse the lazy checks):

  function basicValidatePassword(password) {
    const minLength = 8;
    const maxLength = 64;
    const isValidChars = /^[A-Za-z0-9]+$/;
    const hasUpperCase = /[A-Z]/;
    const hasLowerCase = /[a-z]/;
    const hasSpecialChar = /[\W_]/;

    const results = {minLength: password.length >= minLength,
      maxLength: password.length <= maxLength,
      hasUpper: hasUpperCase.test(password),
      hasLower: hasLowerCase.test(password),
      hasSpecial: hasSpecialChar.test(password),
      hasValidChars: isValidChars.test(password)}
    results.isValid = Object.values(results).every(item => item);

    return results;
  }

Then instead of writing another one on the server that only checks the password isn't blank, is less than the maximum, and has valid characters you're just reusing the full 6 check code. That's only twice as many checks, not even twice as many lines, and it's already written. You really should check all 6 again on the server anyways, but that's beside the point. Better still, if you do the reuse as a build step via shared function library file or similar you don't need to copy/paste and it stays in sync automatically.

Of particular note there is no UI code here because the meter's UI code is not related to the check function beyond it reads the return value.

Why make a round trip if you don’t have to?