Electron Desktop App Development · Leçon

Stockage local et IndexedDB

Utilisez des mécanismes de stockage semblables à ceux des navigateurs, comme `localStorage` et `IndexedDB`, pour assurer la persistance des données côté client dans votre application Electron.

Stockage local et IndexedDB est une leçon Electron Desktop App Development gratuite sur CoddyKit. Ceci est la leçon 1 sur 3. Tu peux lire la leçon complète ci-dessous gratuitement — puis la pratiquer en direct dans le navigateur avec un éditeur de code intégré et un tuteur IA 24/7. Elle fait partie du parcours d'apprentissage Electron Desktop App Development, et ta progression se synchronise sur le web et l'application CoddyKit. Le cours Electron Desktop App Development comprend 3 leçons au total.

Certaines parties de cette leçon n'ont pas encore été traduites et s'affichent en anglais.

Saving Data in Electron Apps

When building desktop applications with Electron, you often need to save user data or application settings. This is called data persistence.

Unlike web apps that rely on servers, Electron apps can store data directly on the user's computer. This lesson explores two common browser-like storage methods: localStorage and IndexedDB.

Introducing Web Storage API

Electron's renderer processes are essentially web browsers. This means you can use standard browser APIs for data storage, like the Web Storage API.

The Web Storage API provides two main types:

localStorage: Stores data with no expiration date.
sessionStorage: Stores data only for the duration of the browser session.

We'll focus on localStorage for persistent data.

Understanding localStorage

localStorage allows you to store data as simple key-value pairs. Think of it like a small, local dictionary.

Persistence: Data stored in localStorage remains even after the app is closed and reopened.
Scope: Data is unique to the origin (your app's domain, usually file:// for Electron).
Capacity: Limited to about 5-10 MB per origin.

It's great for small amounts of data like user preferences or simple settings.

Storing Data with localStorage

You can store data in localStorage using the setItem() method. Remember, values are always stored as strings.

Try running this example in your renderer process:

/* This code runs in the Electron renderer process. */

const username = "CoddyKitUser";
localStorage.setItem("userName", username);

const userSettings = {
  theme: "dark",
  notifications: true
};
// Objects need to be converted to JSON strings
localStorage.setItem("appSettings", JSON.stringify(userSettings));

console.log("Data saved to localStorage!");

Retrieving & Removing localStorage Data

To get data back, use getItem(). To delete, use removeItem(). If you stored an object, you'll need to parse it back from JSON.

Run this snippet after the previous one:

/* This code runs in the Electron renderer process. */

const storedUsername = localStorage.getItem("userName");
console.log("Stored Username:", storedUsername);

const storedSettingsString = localStorage.getItem("appSettings");
if (storedSettingsString) {
  const storedSettings = JSON.parse(storedSettingsString);
  console.log("Stored Theme:", storedSettings.theme);
}

// To remove an item:
localStorage.removeItem("userName");
console.log("Username removed.");

// To clear all localStorage for the origin:
// localStorage.clear();

Limitations of localStorage

While easy to use, localStorage has some limitations:

Size Limit: Typically 5-10 MB per origin. Not suitable for large datasets.
String-Only: All data is stored as strings. Objects and arrays must be manually serialized (e.g., with JSON.stringify()) and deserialized (JSON.parse()).
Synchronous: Operations block the main thread, which can cause UI freezes if you're storing/retrieving a lot of data.
No Indexing/Querying: You can't directly query data, only access by key.

Introducing IndexedDB

For larger, more structured, and complex data, IndexedDB is a powerful alternative. It's a low-level API for client-side storage of significant amounts of structured data.

No Size Limit: Generally limited only by available disk space.
Structured Data: Can store JavaScript objects directly, not just strings.
Asynchronous: Operations don't block the UI thread, making it suitable for performance-critical apps.

IndexedDB Core Concepts

IndexedDB works with a few key concepts:

Databases: You create databases, each with a name and version.
Object Stores: Like tables in a relational database, but they store JavaScript objects. Each object store has a key path.
Indexes: For fast querying of data within an object store.
Transactions: All read and write operations must occur within a transaction, ensuring data integrity.
Asynchronous: Operations return IDBRequest objects, which resolve with success or error events (or Promises).

Basic IndexedDB Setup

Setting up IndexedDB involves opening a database and defining object stores. This is usually done in the renderer process.

This example shows how to open a database and create an object store if it doesn't exist:

/* This code runs in the Electron renderer process. */

const request = indexedDB.open("CoddyKitDB", 1); // DB name, version

request.onerror = (event) => {
  console.error("Database error:", event.target.errorCode);
};

request.onsuccess = (event) => {
  const db = event.target.result;
  console.log("Database opened successfully!");
  // You can now interact with the database (add/get data)
  db.close(); // Close when done if not actively using
};

request.onupgradeneeded = (event) => {
  // This runs if the database didn't exist or version changed
  const db = event.target.result;
  const objectStore = db.createObjectStore("users", { keyPath: "id" });
  console.log("Object store 'users' created.");
  // You can also create indexes here
  objectStore.createIndex("name", "name", { unique: false });
};

Quick Check on Storage

You've learned about localStorage and IndexedDB. Which statement accurately describes a key difference?

Recap: Local & IndexedDB

Great job! You've explored client-side data persistence in Electron:

localStorage is simple, synchronous, key-value storage for small, non-critical data.
IndexedDB is a powerful, asynchronous, transactional database for large amounts of structured data.

Choosing between them depends on your data's size, structure, and performance needs. Both are crucial for building robust Electron applications that save user data locally.

Questions Fréquemment Posées

La leçon « Stockage local et IndexedDB » est-elle gratuite ?

Oui — le texte complet de « Stockage local et IndexedDB » est gratuit à lire ici sur le web. Pour la pratiquer de manière interactive (un éditeur de code intégré et un tuteur IA 24/7) et déverrouiller le reste du cours Electron Desktop App Development, passe à CoddyKit PRO. Le cours Electron Desktop App Development comprend 3 leçons au total.

Qu'est-ce que j'apprendrai dans « Stockage local et IndexedDB » ?

Utilisez des mécanismes de stockage semblables à ceux des navigateurs, comme `localStorage` et `IndexedDB`, pour assurer la persistance des données côté client dans votre application Electron. Tu pratiques Electron Desktop App Development avec du code pratique que tu exécutes directement dans le navigateur, et un tuteur IA 24/7 répond à tes questions au fur et à mesure que tu avances dans la leçon.

Dois-je avoir de l'expérience pour commencer Electron Desktop App Development ?

Aucune expérience préalable n'est requise. Electron Desktop App Development sur CoddyKit est structuré pour les débutants jusqu'aux apprenants avancés, donc tu peux commencer ici ou depuis le début et avancer à ton rythme. Ceci est la leçon 1 sur 3.

Combien de temps prend la leçon « Stockage local et IndexedDB » ?

La plupart des leçons CoddyKit prennent environ 5–10 minutes. Chacune est courte et interactive, tu progresses régulièrement et tu repiques exactement où tu t'es arrêté sur le web et l'app.

Peux-tu écrire et exécuter du code dans cette leçon Electron Desktop App Development ?

Oui. Chaque leçon Electron Desktop App Development inclut un éditeur de code intégré, tu écris et exécutes du vrai code directement dans ton navigateur et tu reçois des retours IA instantanés — aucune configuration locale requise.

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