Saving & Loading

SaveManager persists named save slots as versioned envelopes. Each save records the schema version it was written at, so a shipped game can change its save shape later and still read old saves — on load, older data is migrated forward.

Save slots

Create one manager for your game (pick a current schema version), then read and write slots by name:

import { SaveManager } from 'esengine';

const saves = new SaveManager({ version: 1 });

saves.save('slot1', { level: 3, score: 1200, hp: 80 });

const data = saves.load<{ level: number; score: number; hp: number }>('slot1');
// -> { level: 3, score: 1200, hp: 80 }   (or null if the slot is empty)

saves.has('slot1');       // true
saves.savedAt('slot1');   // epoch ms the slot was written, or null
saves.remove('slot1');    // delete the slot

save(slot, data) writes data stamped with the current version and time.
load(slot) returns the slot’s data (migrated forward), or null when the slot is empty or unreadable.
has / remove / savedAt query, delete, and timestamp a slot.

Schema migration

When your save shape changes, bump version and add a migration for each step. migrations[n] upgrades a save written at version n to n + 1; on load, every step from the save’s version up to the current one runs in order:

const saves = new SaveManager({
  version: 2,
  migrations: {
    // v1 stored a flat score; v2 nests it under `stats`.
    1: (old) => {
      const s = old as { level: number; score: number };
      return { level: s.level, stats: { score: s.score, deaths: 0 } };
    },
  },
});

// A v1 save on disk is upgraded to the v2 shape transparently on load.
const data = saves.load('slot1');

Migration is forward-only: loading a save that is newer than the current version throws (no downgrade), and a missing step in the chain throws too — so a gap is caught immediately instead of silently corrupting data.

Plain key/value storage

For simple flags and preferences that don’t need versioning, use the Storage API directly — a per-platform key/value store (browser localStorage, WeChat storage, …) with typed helpers:

import { Storage } from 'esengine';

Storage.setBoolean('muted', true);
Storage.setNumber('volume', 0.8);
Storage.setJSON('keybinds', { jump: 'Space', fire: 'KeyJ' });

Storage.getBoolean('muted', false);   // true
Storage.getNumber('volume', 1);       // 0.8
Storage.has('keybinds');              // true

Storage also has getString / setString, remove(key), and clear(). SaveManager is built on top of it, so both persist to the same per-platform backend.