const form = {
  account: '',
}

const schema = {
  account: {
    $params: {
      languageCode: 'en',
      minLength: 6,
    },

    $normalizer({ value, key, parent, path, root, params }) {
      return typeof value === 'string' ? value.trim() : ''
    },

    $rules: {
      weak({ value, key, parent, path, root, params }) {
        if (value.length < params.minLength) return 'Too short'
        if (/\W/.test(value)) return 'Must contain special charachar'
      },

      async alreadyBeenUsed({ value, key, parent, path, root, params }) {
        if (value === '') return

        if (await isExists(value)) return false
      },
    },

    $errors: {
      weak({ value, key, parent, path, root, params }) {
        return params.$rules.weak
      },

      alreadyBeenUsed({ value, key, parent, path, root, params }) {
        const languageCode = params.languageCode || 'en-US'
        return translate(`This account has already been used.`, { languageCode })
      },
    },
  },
}

const validator = {}

// in order to track form's data sctructure (e.g., add new property to object, or push new element to array), you should always update your fields from the proxiedForm instead of the original form
const proxiedForm = FormValidation.proxy({ form, schema, validator })

// validate the entire form
await validator.$v.validate()

console.log(validator.$v.invalid)
// > true
console.log(validator.$v.errors.weak)
// > 'Too short.'