Store

Some state should survive page reloads—user preferences, form drafts, cart contents. state() is reactive but resets when the user refreshes. Store wraps state() with persistence: you define which parts go to localStorage (saved), sessionStorage (tab), or stay volatile (temporary). Call store.save() when you want to persist; on load, Store hydrates from storage. During SSR, Store skips storage and hydrates from serialized state.

Typical use. Create a Store, call load(saved, temporary, tab) with template objects. The first argument defines what persists to localStorage; the second is volatile; the third goes to sessionStorage (survives reload, clears when the tab closes). Access store.state like state()—properties are reactive. Call ready() after load if you have computed properties that depend on other app state (e.g. $s, routes). For SSR, pass a fourth session template and hydrate from the server.

import m, {Store, MithrilComponent} from '@bitstillery/mithril'

const store = new Store<{count: number}>()
store.load({count: 0}, {}, {}) // saved, temporary, tab — count persists to localStorage

class App extends MithrilComponent {
    view() {
        return (
            <div>
                <p>Count: {store.state.count} (persists across reloads)</p>
                <button
                    onclick={() => {
                        store.state.count++
                        store.save()
                    }}
                >
                    Increment
                </button>
            </div>
        )
    }
}

m.mount(document.getElementById('app'), App)

load(saved, temporary, tab, session?) — Merge templates; restore from localStorage/sessionStorage (or SSR payload). saved → localStorage, tab → sessionStorage, temporary → volatile.
save() — Persist current state to storage. Call after user actions (e.g. login, filter change, cart update).
blueprint(state, template) — Extract a subset of state for persistence; used internally by save().
ready() — Enable computed properties (call after load when computeds depend on app context).
During SSR, Store skips localStorage/sessionStorage and hydrates from serialized state injected by the server.