useState
The useState composable creates a reactive and SSR-friendly shared state.
Usage
// Create a reactive state and set default value
const count = useState('counter', () => Math.round(Math.random() * 100))
Because the data inside
useState
will be serialized to JSON, it is important that it does not contain anything that cannot be serialized, such as classes, functions or symbols.useState
is a reserved function name transformed by the compiler, so you should not name your own function useState
.Using shallowRef
If you don't need your state to be deeply reactive, you can combine useState
with shallowRef
. This can improve performance when your state contains large objects and arrays.
const state = useState('my-shallow-state', () => shallowRef({ deep: 'not reactive' }))
// isShallow(state) === true
Type
useState<T>(init?: () => T | Ref<T>): Ref<T>
useState<T>(key: string, init?: () => T | Ref<T>): Ref<T>
key
: A unique key ensuring that data fetching is properly de-duplicated across requests. If you do not provide a key, then a key that is unique to the file and line number of the instance ofuseState
will be generated for you.init
: A function that provides initial value for the state when not initiated. This function can also return aRef
.T
: (typescript only) Specify the type of state