sessionStorage (a storage that persists for duration of the session, comparable to session cookies)

localStorage (a persistent storage, which can be compared to persistent cookies)

class Session extends Map { set(id, value) { if (typeof value === 'object') value = JSON.stringify(value); sessionStorage.setItem(id, value); } get(id) { const value = sessionStorage.getItem(id); try { return JSON.parse(value); } catch (e) { return value; } } }

The Web Storage API provides mechanisms by which browsers can store key/value pairs, in a much more intuitive fashion than using cookies.

const store = observable({ players: [ "Player 1", "Player 2", ], // ... }) reaction(() => JSON.stringify(store), json => { localStorage.setItem('store',json); }, { delay: 500, }); let json = localStorage.getItem('store'); if(json) { Object.assign(store, JSON.parse(json)); }