LocalStorage

localStorage is a feature of the [[Web Storage API]] provided by modern web browsers that allows websites and applications to store data in the user's browser. This data is stored across browser sessions, meaning it persists even after the browser is closed and reopened.

localStorage is used for storing key-value pairs on the client side and is accessible only by web pages from the same origin (same protocol, domain, and port).

Unlike [[sessionStorage]], which is cleared when the browsing session ends (i.e., when the browser tab is closed), localStorage retains data even after the browser is closed and reopened. Data stored in localStorage is specific to the document's origin and is accessible only to pages from the same origin.

localStorage typically offers a significant amount of storage space (often around 5-10 MB per origin), much more than what cookies provide. localStorage operations are synchronous, meaning they occur in the order they are called. This can impact performance when dealing with large amounts of data or high-frequency read/write operations.

localStorage is ideal for saving user preferences, such as theme or layout choices, that should persist across browser sessions. It can be used to cache data locally to improve load times and reduce the need for repeated server requests. localStorage helps in maintaining the state of web applications or games without needing to send data back to the server.

An example usage:

// Storing data in localStorage
localStorage.setItem('key', 'value');

// Retrieving data from localStorage
let data = localStorage.getItem('key');

// Removing data from localStorage
localStorage.removeItem('key');

// Clearing all data from localStorage
localStorage.clear();

In this JavaScript example, data is stored in localStorage using setItem, retrieved with getItem, removed with removeItem, and all data in localStorage can be cleared with clear.