validate.js

module.exports = {
  /**
   * Function to verify all validations
   * @param  {...any} paramsRaw An array of validation results,
   * Values can either be `true` or `error string`.
   */
  all: async function (...paramsRaw) {
    const params = await Promise.all(paramsRaw)
    const error = params
      .filter(val => typeof val === 'string')[0]

    if (error) {
      return Promise.reject(error)
    }
  },
  maxLength: function (maxLen, paramOb) {
    const failedEntries = Object.keys(paramOb)
      .filter(key => String(paramOb[key] || '').length > maxLen)
    
    if (failedEntries.length) {
      const errorMessage = `'${failedEntries.join(', ')}' exceed the limit`
      return errorMessage
    }

    return true
  },
  notEmpty: function (paramOb) {
    const failedEntries = Object.keys(paramOb)
      .filter(key => !paramOb[key])
    
    if (failedEntries.length) {
      const errorMessage = `'${failedEntries.join(', ')}' cannot be empty`
      return errorMessage
    }

    return true
  }
}