How to use

normalizeUsername

function

in

lodash

function UsernameExtension(joi) {
 return {
  base: joi.string(),
  name: 'string',
  language: {
   invalidUsername: 'must contains only letters and digits'
  },
  rules: [
   {
    name: 'isUsername',
    validate(params, value, state, options) {
     if (!validationRules.user.username.regExp.test(value)) {
      return this.createError('string.invalidUsername', { value }, state, options);
     }
     return normalizeUsername(value);
    }
   }
  ]
 };
}