@larscom/ngrx-signals-storage
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Save signal state (@ngrx/signals) to localstorage/sessionstorage and restore the state on page load (with SSR support).
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# @larscom/ngrx-signals-storage
[](https://www.npmjs.com/package/@larscom/ngrx-signals-storage)
[](https://github.com/larscom/ngrx-signals-storage/blob/main/LICENSE)
> Save signal state (@ngrx/signals) to localStorage/sessionStorage and restore the state on page load with a single line of code (with SSR support).
## Installation
```bash
npm install @larscom/ngrx-signals-storage
```
## Dependencies
`@larscom/ngrx-signals-storage` depends on [@ngrx/signals](https://ngrx.io/guide/signals/install) and [Angular](https://github.com/angular/angular)
## Usage
Import the `withStorage` function and place it after the `withState` function. Optional configuration can be passed as 3th argument.
```ts
import { withStorage } from '@larscom/ngrx-signals-storage'
import { withState, signalStore } from '@ngrx/signals'
export const CounterStore = signalStore(
withState({
count: 0
}),
// state will be saved to sessionStorage under the key: 'myKey'
withStorage('myKey', () => sessionStorage)
)
```
## Configuration
```ts
export interface Config<T> {
/**
* These keys will not get saved to storage
*/
excludeKeys: Array<keyof T>
/**
* Serializer for the state, by default it uses `JSON.stringify()`
* @param state the last state known before it gets saved to storage
*/
serialize: (state: T) => string
/**
* Deserializer for the state, by default it uses `JSON.parse()`
* @param state the last state known from the storage location
*/
deserialize: (state: string) => T
/**
* Save to storage will only occur when this function returns true
* @param state the last state known before it gets saved to storage
*/
saveIf: (state: T) => boolean
/**
* Function that gets executed on a storage error (get/set)
* @param error the error that occurred
*/
error: (error: any) => void
}
```
## Save conditionally
Sometimes you only want to save to storage on a specific condition.
```ts
import { withStorage } from '@larscom/ngrx-signals-storage'
import { withState, signalStore } from '@ngrx/signals'
export const CounterStore = signalStore(
withState({
count: 0
}),
// save only occurs when count is higher than 0
withStorage('myKey', () => sessionStorage, { saveIf: ({ count }) => count > 0 })
)
```
## Skip properties
Sometimes you want to ignore / exclude properties so they do not get saved into storage. On page reload, the initial value will be loaded instead.
```ts
import { withStorage } from '@larscom/ngrx-signals-storage'
import { withState, signalStore } from '@ngrx/signals'
export const CounterStore = signalStore(
withState({
count: 0,
sum: 0
}),
// sum does not get saved into sessionStorage.
withStorage('myKey', () => sessionStorage, { excludeKeys: ['sum'] })
)
```
## Common Errors
Whenever you get errors this is most likely due to serialization / deserialization of the state.
Objects like `Map` and `Set` are not serializable so you might need to implement your own serialize / deserialize function.
### Serialize / Deserialize
Lets say you have a `Set` in your store, then you need a custom serialize / deserialize function to convert from `Set` to `Array` (serialize) and from `Array` to `Set` (deserialize)
```ts
export const MyStore = signalStore(
withState({
mySet: new Set([1, 1, 3, 3])
}),
withStorage('myKey', () => sessionStorage, {
serialize: (state) => JSON.stringify({ ...state, mySet: Array.from(state.mySet) }),
deserialize: (stateString) => {
const state = JSON.parse(stateString)
return {
...state,
mySet: new Set(state.mySet)
}
}
})
)
```