Svelte 5 persisted states, svelte-persisted-store, but implemented with Svelte 5 Runes.
This package requires Svelte 5. It is not compatible with Svelte 4 or earlier versions.
npm install svelte-persisted-stateimport { persistedState } from 'svelte-persisted-state';
const myState = persistedState('myKey', 'initialValue');
// Use myState.value to get or set the state
console.log(myState.value);
myState.value = 'newValue';
// Reset to initial value
myState.reset();import { persistedState } from 'svelte-persisted-state';
interface UserPreferences {
theme: 'light' | 'dark';
fontSize: number;
notifications: boolean;
}
const userPreferences = persistedState<UserPreferences>(
'userPreferences',
{
theme: 'light',
fontSize: 16,
notifications: true
},
{
storage: 'local',
syncTabs: true,
beforeWrite: (value) => {
console.log('Saving preferences:', value);
return value;
},
onWriteError: (error) => {
console.error('Failed to save preferences:', error);
}
}
);
// Usage in a Svelte component
function toggleTheme() {
userPreferences.value = {
...userPreferences.value,
theme: userPreferences.value.theme === 'light' ? 'dark' : 'light'
};
}
// This is also valid
function toggleTheme() {
userPreferences.value.theme = userPreferences.value.theme === 'light' ? 'dark' : 'light'
}
// Using $derived for reactive computations
const theme = $derived(userPreferences.value.theme);
// The UI will automatically update when the state changesThe persistedState function creates a persisted state that automatically syncs with local or session storage.
key: A string key used for storage.initialValue: The initial value of the state.options: An optional object with the following properties:storage: 'local' (default) or 'session'serializer: Custom serializer object withparseandstringifymethodssyncTabs: Boolean to sync state across tabs (default: true)onWriteError: Function to handle write errorsonParseError: Function to handle parse errorsbeforeRead: Function to process value before readingbeforeWrite: Function to process value before writing
The persistedState function returns an object with the following properties:
value: Get or set the current state value.reset(): Reset the state to its initial value.
<script lang="ts">
import { persistedState } from 'svelte-persisted-state';
interface UserPreferences {
theme: 'light' | 'dark';
fontSize: number;
}
const preferences = persistedState<UserPreferences>('preferences', {
theme: 'light',
fontSize: 16
});
const theme = $derived(preferences.value.theme);
const fontSize = $derived(preferences.value.fontSize);
function toggleTheme() {
preferences.value = {
...preferences.value,
theme: theme === 'light' ? 'dark' : 'light'
};
}
function decreaseFontSize() {
preferences.value = {
...preferences.value,
fontSize: fontSize - 1
};
}
function increaseFontSize() {
preferences.value = {
...preferences.value,
fontSize: fontSize 1
};
}
</script>
<div style="font-size: {fontSize}px">
<button onclick={toggleTheme}>
Switch to {theme === 'light' ? 'dark' : 'light'} theme
</button>
<button onclick={decreaseFontSize}> Decrease font size </button>
<button onclick={increaseFontSize}> Increase font size </button>
<p>Current theme: {theme}</p>
<p>Current font size: {fontSize}px</p>
</div><script lang="ts">
import { persistedState } from 'svelte-persisted-state';
interface UserPreferences {
theme: 'light' | 'dark';
fontSize: number;
}
const preferences = persistedState<UserPreferences>('preferences', {
theme: 'light',
fontSize: 16
});
const theme = $derived(preferences.value.theme);
const fontSize = $derived(preferences.value.fontSize);
</script>
<div style="font-size: {fontSize}px">
<button onclick={() => (preferences.value.theme = theme === 'light' ? 'dark' : 'light')}>
Switch to {theme === 'light' ? 'dark' : 'light'} theme
</button>
<button onclick={() => (preferences.value.fontSize = fontSize - 1)}> Decrease font size </button>
<button onclick={() => (preferences.value.fontSize = fontSize 1)}> Increase font size </button>
<p>Current theme: {theme}</p>
<p>Current font size: {fontSize}px</p>
</div>MIT