Valdres

selector

Signature
selector<T>(getter: (get: GetFn) => T): Selector<T>

valdres Derive computed state that updates automatically

Creates derived state that automatically recomputes when its dependencies change. Selectors are read-only — they compute their value from atoms and other selectors.

Usage

import { atom, selector } from "valdres"

const firstNameAtom = atom("John")
const lastNameAtom = atom("Doe")

const fullNameSelector = selector(get => {
    const first = get(firstNameAtom)
    const last = get(lastNameAtom)
    return `${first} ${last}`
})

Parameters

ParameterTypeDescription
getter(get: GetFn) => TA function that computes the derived value. Use get() to read atoms or other selectors.

Async selectors

Selectors can also be async. They work with Suspense in React.

const userDataSelector = selector(async get => {
    const userId = get(userIdAtom)
    const res = await fetch(`/api/users/${userId}`)
    return res.json()
})

See also

  • selectorFamily — create a collection of selectors keyed by a parameter
  • useValue — read a selector value in your components