Web Storage: LocalStorage & SessionStorage

Persisting user state and data on the client device

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With Web Storage, web applications can store data locally within the user's browser with no expiration date (unlike cookies which have size limits and expire).

localStorage in Practice

localStorage.setItem("key", "value"): Stores an item.

localStorage.getItem("key"): Retrieves an item.

localStorage.removeItem("key"): Removes a single item.

JSON.stringify() and JSON.parse(): Enables saving complex objects and arrays into localStorage strings.

Saving and Retrieving State

Try It Yourself »

// Saving complex data
const userSession = {
  theme: "dark",
  lastLesson: "javascript/async-await",
  completedCount: 14
};

localStorage.setItem("codexia_session", JSON.stringify(userSession));

// Retrieving data
const stored = localStorage.getItem("codexia_session");
if (stored) {
  const parsed = JSON.parse(stored);
  console.log("Welcome back! Active theme:", parsed.theme);
}

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Set your Publisher ID in src/config/ads.ts to display live ads.

Test Yourself With Exercise

+15 XP

Which method converts a JavaScript object into a JSON string suitable for localStorage?

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