STORAGE API /// LOCAL PERSISTENCE /// CLIENT SIDE DB /// NO COOKIES /// STORAGE API /// LOCAL PERSISTENCE /// CLIENT SIDE DB /// NO COOKIES /// STORAGE API /// LOCAL PERSISTENCE /// CLIENT SIDE DB /// NO COOKIES ///

HTML5 LocalStorage

Persist data in the browser. Store strings, handle JSON, and manage user state without a database.

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Tutor:LocalStorage allows web applications to store data locally within the user's browser. Unlike cookies, the storage limit is larger (at least 5MB) and information is never transferred to the server.


Storage Matrix

UNLOCK NODES BY MASTERING APIs.

Concept: Saving

Data persists until explicitly deleted. Use setItem(key, val) to save.

System Check

Does LocalStorage data expire when you close the browser?

Community Holo-Net

Persistence hacks

ACTIVE

Built a theme switcher or a todo list using LocalStorage? Share your implementation details.

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HTML5 LocalStorage

Author

Pascual Vila

Frontend Instructor // Code Syllabus

LocalStorage is part of the Web Storage API. It allows web applications to store data locally within the user's browser with no expiration date.

Storing Data

The primary method is setItem(key, value). It takes a key (identifier) and a value (content). Both must be strings. If you need to store objects, you must serialize them first.

Retrieving Data

To read data back, use getItem(key). If the key exists, the string value is returned. If not, it returns null.

Cleaning Up

You can remove a specific item using removeItem(key) or wipe the entire storage for the domain using clear().

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This section covers the Web Storage API details, including the 5MB storage limit, the synchronous nature of the API (blocking the main thread), and security considerations regarding XSS attacks.

Storage API Glossary

localStorage.setItem()
Stores a value associated with a key. If the key exists, it updates the value. Everything is stored as a string.
localStorage.getItem()
Retrieves the value for a specific key. Returns null if the key doesn't exist in the storage object.
JSON.stringify()
Converts JavaScript objects or arrays into a JSON string, essential before saving complex data to storage.
JSON.parse()
Converts a JSON string back into a JavaScript object, allowing you to access properties after retrieval.
localStorage.removeItem()
Deletes a specific entry from the storage object based on the provided key.
localStorage.clear()
Nuclear option: wipes ALL key/value pairs belonging to your domain's storage.