validatorjs/validator.js · error · Error

Invalid locale '${locale}'

Error message

Invalid locale '${locale}'

What it means

isAlphanumeric(str, locale) tests against per-locale regexes keyed exactly like the alpha table (e.g. 'en-US', 'ar-SA'). An unknown locale key throws this error rather than returning false, to fail fast on misconfiguration.

Source

Thrown at src/lib/isAlphanumeric.js:23

  assertString(_str);

  let str = _str;
  const { ignore } = options;

  if (ignore) {
    if (ignore instanceof RegExp) {
      str = str.replace(ignore, '');
    } else if (typeof ignore === 'string') {
      str = str.replace(new RegExp(`[${ignore.replace(/[-[\]{}()*+?.,\\^$|#\\s]/g, '\\$&')}]`, 'g'), ''); // escape regex for ignore
    } else {
      throw new Error('ignore should be instance of a String or RegExp');
    }
  }

  if (locale in alphanumeric) {
    return alphanumeric[locale].test(str);
  }
  throw new Error(`Invalid locale '${locale}'`);
}

export const locales = Object.keys(alphanumeric);

View on GitHub (pinned to a79ff980ab)

Solutions

1. Pick the locale from the module's exported locales list
2. Map application locales to validator locale keys before calling
3. Default to 'en-US' when the configured locale is unsupported
4. Inspect the runtime value when the message shows 'undefined' or empty

Example fix

// before
const loc = req.acceptsLanguages()[0]; // e.g. 'en'
validator.isAlphanumeric(input, loc); // throws
// after
const map = { en: 'en-US', ar: 'ar-EG' };
validator.isAlphanumeric(input, map[loc.split('-')[0]] || 'en-US');

import { locales as alnumLocales } from 'validator';
if (!alnumLocales.includes(locale)) locale = 'en-US';

const isValidAlphanumericLocale = (loc) => typeof loc === 'string' && alnumLocales.includes(loc);

let ok;
try { ok = validator.isAlphanumeric(str, locale); }
catch (e) { if (/^Invalid locale/.test(e.message)) { ok = validator.isAlphanumeric(str, 'en-US'); } else { throw e; } }

When it happens

Trigger: isAlphanumeric('foo123', 'en') instead of 'en-US'; empty-string or undefined locale interpolated into the message; a locale key removed in a library upgrade.

Common situations: Hard-coded two-letter codes from i18n config; dynamic locale from HTTP Accept-Language passed raw; environment-specific config leaving the variable unset.

Related errors

• Invalid locale '${locale}'
• Invalid locale '${options.locale}'
• ignore should be instance of a String or RegExp
• ignore should be instance of a String or RegExp
• ${provider} is not a valid credit card provider.

AI-assisted analysis of validatorjs/validator.js@a79ff980ab (2026-08-31). Data as JSON: /api/errors/8de9105c211f0c81. Report an issue: GitHub.