import {createEvent, createStore, forward} from 'effector'

​

const punch = createEvent()

const veryStrongHit = createEvent()

​

const $lastPunchStrength = createStore(0, {

  // If store should be updated with strength less than 400 kg

  // update will be skipped

  updateFilter: strength => strength >= 400,

})

​

$lastPunchStrength.on(punch, (_, strength) => strength)

​

// Each store update should trigger event `veryStrongHit`

forward({from: $lastPunchStrength, to: veryStrongHit})

​

// Watch on store prints initial state

$lastPunchStrength.watch(strength => console.log('Strength: %skg', strength))

// => Strength: 0kg

​

veryStrongHit.watch(strength => {

  console.log('Wooow! It was very strong! %skg', strength)

})

​

punch(200) // updateFilter prevented update

punch(300) // Same here. Note: store don't updates, value is the same `0`

punch(500) // Yeeah! updateFilter allows to update store value

// => Strength: 500kg

// => Wooow! It was very strong! 500kg

punch(100) // Also nothing

​