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[note] jotai 筆記

TL;DR​

import { atom, useAtom, useAtomValue } from 'jotai';
import { useAtomValue, useUpdateAtom } from 'jotai/utils'

const isEditingAtom = atom(false);

const App = () => {
  // normal usage
  const [isEditing, setIsEditing] = useAtom(countAtom)

  // if only need the setter
  // useUpdateAtom can prevent unnecessary re-render
  const setIsEditing = useUpdateAtom(isEditingAtom);

  // if only need the getter
  const isEditing = useAtomValue(isEditingAtom);
}

MISC​

Resettable​

resettable @ jotai > guides

使用 atomWithReset 和 useResetAtom 可以把取得一個 function 來把 atom 設回 default value：

const todoListAtom = atomWithReset([{ description: 'Add a todo', checked: false }])

const TodoList = () => {
  const [todoList, setTodoList] = useAtom(todoListAtom)
  const resetTodoList = useResetAtom(todoListAtom)

  return <button onClick={resetTodoList}>Reset</button>;
}

Good Discussion​

如果想要在 render 時不透過 useEffect 設定 atom 的初始值​

Can an atom be initialized on the first render? @ Github Discussion

// https://github.com/pmndrs/jotai/discussions/581#discussioncomment-972361

const fooAtom = atom(null)

const ParentComponent = ({ foo }) => (
  <Provider initialValues={[[fooAtom, foo]]}>
    <ChildComponent />
  </Provider>
)

const ChildComponent = () => {
  const [foo, setFoo] = useAtom(fooAtom)
  // foo is already initialized.
}