useSetAtom

import { atom, useSetAtom, useAtomValue } from 'jotai'

const switchAtom = atom(false)

const SetTrueButton = () => {
  const setCount = useSetAtom(switchAtom)
  const setTrue = () => setCount(true)

  return (
    <div>
      <button onClick={setTrue}>Set True</button>
    </div>
  )
}

const SetFalseButton = () => {
  const setCount = useSetAtom(switchAtom)
  const setFalse = () => setCount(false)

  return (
    <div>
      <button onClick={setFalse}>Set False</button>
    </div>
  )
}

export default function App() {
  const state = useAtomValue(switchAtom)

  return (
    <div className="App">
      State: <b>{state.toString()}</b>
      <SetTrueButton />
      <SetFalseButton />
    </div>
  )
}

In case you create a write only atom where the value never changes you can use the useSetAtom hook. useSetAtom is premature optimization in this scenario.

For primitive values if you use const [, setValue] = useAtom(valueAtom) it can cause unnecessary re-renders, so useSetAtom helps to avoid those extra re-renders.