is

Namespace for unit validators

is.store(value)

Checks if given value is store

Returns

boolean

import {
  is,
  createStore,
  createEvent,
  createEffect,
  createDomain,
} from 'effector'

const $store = createStore(null)
const event = createEvent()
const fx = createEffect()

is.store($store)
// => true

is.store(event)
// => false

is.store(fx)
// => false

is.store(createDomain())
// => false

is.store(fx.pending)
// => true

is.store(fx.done)
// => false

is.store($store.updates)
// => false

is.store(null)
// => false

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is.event(value)

Checks if given value is event

Returns

boolean

import {
  is,
  createStore,
  createEvent,
  createEffect,
  createDomain,
} from 'effector'

const $store = createStore(null)
const event = createEvent()
const fx = createEffect()

is.event($store)
// => false

is.event(event)
// => true

is.event(fx)
// => false

is.event(createDomain())
// => false

is.event(fx.pending)
// => false

is.event(fx.done)
// => true

is.event($store.updates)
// => true

is.event(null)
// => false

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is.effect(value)

Checks if given value is effect

Returns

boolean

import {
  is,
  createStore,
  createEvent,
  createEffect,
  createDomain,
} from 'effector'

const $store = createStore(null)
const event = createEvent()
const fx = createEffect()

is.effect($store)
// => false

is.effect(event)
// => false

is.effect(fx)
// => true

is.effect(createDomain())
// => false

is.effect(null)
// => false

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is.domain(value)

Checks if given value is domain

Returns

boolean

import {
  is,
  createStore,
  createEvent,
  createEffect,
  createDomain,
} from 'effector'

const $store = createStore(null)
const event = createEvent()
const fx = createEffect()

is.domain($store)
// => false

is.domain(event)
// => false

is.domain(fx)
// => false

is.domain(createDomain())
// => true

is.domain(null)
// => false

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is.scope(value)

since

effector 22.0.0

Checks if given value is scope

Returns

boolean

import {fork} from 'effector'

const $store = createStore(null)
const event = createEvent()
const fx = createEffect()
const scope = fork()

is.scope(scope)
// => true

is.scope($store)
// => false

is.scope(event)
// => false

is.scope(fx)
// => false

is.scope(createDomain())
// => false

is.scope(null)
// => false

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is.unit(value)

Checks if given value is unit: store, event, effect, domain or scope

Returns

boolean

import {
  is,
  createStore,
  createEvent,
  createEffect,
  createDomain,
  fork,
} from 'effector'

const $store = createStore(null)
const event = createEvent()
const fx = createEffect()
const scope = fork()

is.unit(scope)
// => true

is.unit($store)
// => true

is.unit(event)
// => true

is.unit(fx)
// => true

is.unit(createDomain())
// => true

is.unit(fx.pending)
// => true

is.unit(fx.done)
// => true

is.unit($store.updates)
// => true

is.unit(null)
// => false

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is.attached(value)

since

effector 22.4.0

Checks if given value is effect created via attach method. If passed not an effect, returns false.

Returns

boolean

import {
  is,
  createStore,
  createEvent,
  createEffect,
  createDomain,
  attach,
} from 'effector'

const $store = createStore(null)
const event = createEvent()
const fx = createEffect()

const childFx = attach({
  effect: fx,
})

is.attached(childFx)
// => true

is.attached(fx)
// => false

is.attached($store)
// => false

is.attached(event)
// => false

is.attached(createDomain())
// => false

is.attached(null)
// => false

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Use case

Sometimes you need to add an error log on effects failures, but only on effects that have been "localized" via attach. If you leave onCreateEffect as it is, without checks, the error log will be duplicated, because it will happen on the parent and the child effect.

import {createDomain, attach, is} from 'effector'

const logFailuresDomain = createDomain()

logFailuresDomain.onCreateEffect(effect => {
  if (is.attached(effect)) {
    effect.fail.watch(({params, error}) => {
      console.warn(
        `Effect "${effect.compositeName.fullName}" failed`,
        params,
        error,
      )
    })
  }
})

const baseRequestFx = logFailuresDomain.createEffect(path => {
  throw new Error(`path ${path}`)
})

const loadDataFx = attach({
  mapParams: () => '/data',
  effect: baseRequestFx,
})

const loadListFx = attach({
  mapParams: () => '/list',
  effect: baseRequestFx,
})

loadDataFx()
loadListFx()

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