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zustand-computed
Advanced tools
zustand-computed is a lightweight, TypeScript-friendly middleware for the state management system Zustand. It's a simple layer which adds a transformation function after any state change in your store.
yarn add zustand-computed
The middleware layer takes in your store creation function and a compute function, which transforms your state into a computed state. It does not need to handle merging states.
import computed from "zustand-computed"
const computeState = (state) => ({
countSq: state.count ** 2,
})
const useStore = create(
computed(
(set) => ({
count: 1,
inc: () => set((state) => ({ count: state.count + 1 })),
dec: () => set((state) => ({ count: state.count - 1 })),
}),
computeState
)
)
With types, the previous example would look like this:
import computed from "zustand-computed"
type Store = {
count: number
inc: () => void
dec: () => void
}
type ComputedStore = {
countSq: number
}
const computeState = (state: Store): ComputedStore => ({
countSq: state.count ** 2,
})
const useStore = create<Store, [["chrisvander/zustand-computed", ComputedStore]]>(
computed(
(set) => ({
count: 1,
inc: () => set((state) => ({ count: state.count + 1 })),
dec: () => set((state) => ({ count: state.count - 1 })),
}),
computeState
)
)
The store can then be used as normal in a React component or via the Zustand API.
function Counter() {
const { count, countSq, inc, dec } = useStore()
return (
<div>
<span>{count}</span>
<br />
<span>{countSq}</span>
<br />
<button onClick={inc}>+1</button>
<button onClick={dec}>-1</button>
</div>
)
}
A fully-featured example can be found under the "example" directory.
By default, when zustand-computed
runs your computeState
function, it tracks accessed variables and does not trigger a computation if one of those variables do not change. This could potentially be problematic if you have nested control flow inside of computeState
, or perhaps you want it to run on all changes regardless of use inside of computeState
. To disable automatic selector detection, you can pass a third opts
variable to the computed
constructor, e.g.
const useStore = create<Store, [["chrisvander/zustand-computed", ComputedStore]]>(
computed((set) => ({
count: 1,
inc: () => set((state) => ({ count: state.count + 1 })),
dec: () => set((state) => ({ count: state.count - 1 }))
}), computeState, { disableProxy: true })
)
Other options include passing a keys
array, which explicitly spell out the selectors which trigger re-computation. You can also pass a custom equalityFn
, such as fast-deep-equal instead of the default zustand/shallow
.
FAQs
A Zustand middleware to create computed states.
The npm package zustand-computed receives a total of 9,389 weekly downloads. As such, zustand-computed popularity was classified as popular.
We found that zustand-computed demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 0 open source maintainers collaborating on the project.
Did you know?
Socket for GitHub automatically highlights issues in each pull request and monitors the health of all your open source dependencies. Discover the contents of your packages and block harmful activity before you install or update your dependencies.
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