Save Data

Accessing the Save Data filesystem

nx.js provides built-in APIs for interacting with the Switch save data filesystem. This allows for two main use cases:

Allows your app to persist its own save data, such as user configuration or game state
Allows your app to interact with save data for other installed applications, i.e. for backup purposes

Persisting data using localStorage

The localStorage API provides a high-level interface for persisting data that is stored in the Switch's save data filesystem. Data stored into local storage is unique across user profiles and individual nx.js apps, and will be persisted across subsequent launches of the app.

The user selection dialog will be shown upon accessing the localStorage object, if the app was not launched with a profile selected.

// Read from the save data filesystem the `lastOpened` value
const lastOpened = localStorage.lastOpened;
 
const lastOpenedString = lastOpened ? new Date(Number(lastOpened)) : 'never';
console.log(`App last opened: ${lastOpenedString}`);
 
// Update the `lastOpened` value to the current timestamp
localStorage.lastOpened = Date.now();

Disabling localStorage

If your application does not need to persist save data, then you can disable the localStorage API by setting the nacp.userAccountSaveDataSize property in package.json to 0:

package.json

{
  "nacp": {
    "userAccountSaveDataSize": "0"
  }
}

When this value is set, accessing localStorage will return undefined. This prevents the profile selector from being shown, if any 3rd party modules attempt to access localStorage.

Accessing save data for other applications

The low-level save data interface allows mounting the save data filesystem for any installed application and for the various types of save data filesystems (account, cache, bcat, etc.).

Use the Switch.Application class to mount a save data filesystem:

import { FsSaveDataType } from '@nx.js/constants';
 
const user = Switch.Profile.current;
const app = Switch.Application.find(app => app.name === 'Super Mario 64');
 
// Attempt to find the save data filesystem
// for the app and current user profile.
let saveData = app.findSaveData(s => {
    return s.type === FsSaveDataType.Account &&
      s.uid[0] === user.uid[0] &&
      s.uid[1] === user.uid[1];
});
 
// If there is no save data associated with
// this user, then create it.
if (!saveData) {
    saveData = app.createProfileSaveDataSync(user);
}
 
// Mount the save data filesystem.
// The returned URL can be used with filesystem operations.
const url = saveData.mount();
 
// Read from save data filesystem.
const data = await Switch.readFile(new URL('state.json', url));
 
// Write to save data filesystem.
// (Be sure to `commit()` changes after a write!)
await Switch.writeFile(
    new URL('state.json', url),
    JSON.stringify({ count: 123 })
);
saveData.commit();

Save Data

Persisting data using localStorage

Disabling localStorage

Accessing save data for other applications

Learn more

Learn more about user profile selection

Learn more about the `Switch.Application` class

On this page