a-smaller-2.js

const email = (query, params) => {
  if (!params.email) return query

  const isValid = isValidEmail(params.email)
  if (!isValid) throw new Error('Invalid email')

  return { ...query, ...{ email: params.email } }
}

const maxAge = (query, params) => {
  const obj = { maxAge: '' }
  if (!params.maxAge) obj.maxAge = JSON.parse(localStorage.getItem('defaultMaxAgeLimit') || '')
  if (params.maxAge && params.maxAge < 25) obj.maxAge = params.maxAge

  return { ...query, ...obj }
}

const limit = (query, params) => {
  if (!params.limit) return query

  return { ...query, ...{ limit: params.limit } }
}


const generateQuery = (params) => {
  let query = {}

  try {
    query = email(query, params)
    query = maxAge(query, params)
    query = limit(query, params)
  } catch(err) {
    // error handing
  }

  return query
}