combine.js

import { combine, createStoreObject } from 'effector'

const $name = createStore('Anton')
const $surname = createStore('Kosykh')

// createStoreObject creates store with object of stores states
const $profile = createStoreObject({
  name: $name,
  surname: $surname
})

// combine accepts the list of stores and callback that combines 'em
const $isValid = combine(
  $name, 
  $surname, 
  (name, surname) => name.length && surname.length
)

console.log($profile.getState()) // { name: 'Anton', surname: 'Kosykh' }
console.log($isValid.getState()) // true