localit

🔥 A lightweight, fully-typed wrapper around the Web Storage API (localStorage / sessionStorage) with expiration support, optional key namespacing, and change event listeners.

✅ Features

• Store/retrieve plain and complex values easily, no JSON.stringify required.
• Expiration time support, you decide how log to cache the data
• Family-based key namespacing
• Listen to changes on individual keys
• No dependencies, <1kB gzipped

📦 Install

npm i localit
# or
yarn add localit
# or
pnpm add localit

🚀 Usage

Import

import { localit } from "localit";

set(key, value, config?)

Store a value in storage.

localit.set("foo", { bar: 42 }, { expiration: "5m" });
localit.set("name", "User123", { family: "user" });
localit.set("list", new Set([1, 2, 3]), { type: sessionStorage });
const tomorrow = new Date();
tomorrow.setDate(tomorrow.getDate() + 1);
localit.set("lasts-a-day", { some: "data" }, { expiration: tomorrow });

Config options:

• type: localStorage (default) or sessionStorage
• family: string to namespace the key (stored as family::key)
• expiration: "Xs", "Xm", "Xh", or "Xd". Also accepts a Date object for a fixed expiration date.

get(key, config?)

Retrieve a value.

const value = localit.get("foo");
const set = localit.get<Set<number>>("list");

If the value has expired, it will be removed and null is returned.

remove(key, config?)

Delete a specific key.

localit.remove("foo");

Also, specify a family for even more control

localit.set('foo', 'bar') // Will be stored with 'foo' as key
localit.set('foo', 'baz' { family: 'bar' }) // Will be stores with 'bar::foo key

localit.remove('foo') // Will detele 'foo' but not 'bar::foo'

clearFamily(family, storage?)

Remove all keys that belong to a given family.

localit.clearFamily("user");
localit.clearFamily("cache", sessionStorage); // Only delete `cache` family in sessionStorage, localStorage keys are kept intact

bust(storage?)

Clear all keys from the given storage (localStorage by default)

localit.bust(); // clears localStorage
localit.bust(sessionStorage); // clears sessionStorage

on(key, callback)

Subscribe to key changes (e.g. via set() or remove()).

localit.on("foo", (newValue) => {
  console.log("foo changed:", newValue);
});

Note: this is not the same as the native storage event—it only triggers within the current context when localit methods are used.

🧪 Example

localit.set("cart", { count: 3 }, { expiration: "2h" });

const cart = localit.get("cart"); // { count: 3 }

localit.on("cart", (val) => {
  console.log("Cart updated:", val);
});

localit.set("cart", { count: 4 }); // logs: Cart updated: { count: 4 }

📚 Types

type ExpirationType =
  | `${number}s`
  | `${number}m`
  | `${number}h`
  | `${number}d`
  | Date;

type LocalitSetConfig = {
  type?: Storage;
  family?: string;
  expiration?: ExpirationType;
};

type LocalitGetConfig = {
  type?: Storage;
  family?: string;
};

🛠 Author

Alejandro Mayol
github.com/alexmayol