Javascript Localstorage

By onjsdev

Dec 12th, 2023

LocalStorage allows websites and web applications to store key-value pairs of data locally on a user's device. It's essentially a way to save data on a user's computer without needing a server or database.

Key Features of LocalStorage


Data saved in LocalStorage persists even after the browser window is closed or the computer is restarted. This makes it ideal for storing information that needs to be remembered across sessions, such as:

  • User preferences (e.g., language, theme)
  • Login state (e.g., whether the user is logged in)
  • Cache data (e.g., frequently accessed images or website content)
  • Temporary data (e.g., information needed for the current session)

Simple To Use

LocalStorage provides an easy-to-use API for storing and retrieving data. It uses simple methods like setItem, getItem, removeItem, and clear to manage data.

No expiration date

Unlike cookies which can have expiration times, data stored in LocalStorage doesn't expire unless it's manually deleted by the user or the application.

Limited storage

Each website has a quota for how much data it can store in LocalStorage. This quota is typically around 5MB per domain.

Key-value based

LocalStorage stores data as key-value pairs. You can store any type of data under a unique key for later retrieval.

How To Use With Javascript

As mentioned above, the localStorage object exposes several methods for storing, retrieving, and managing data:

Storing Data

localStorage.setItem("key", "value");

This stores the value "value" under the key "key".

Retrieving Data

const value = localStorage.getItem("key");

This retrieves the value associated with the key "key".

Removing Data


This removes the data associated with the key "key".

Clearing All Data


This clears all data stored in localStorage.

Checking if a key exists

const exists = localStorage.hasOwnProperty("key");

This returns true if the key "key" exists in localStorage, otherwise false.

Practical Examples

Here are some practical examples of how to use localstorage in action:

  • Store user preferences: You can store user preferences like language, theme, or other settings in localStorage for future visits.
  • Save user input: You can save user input in forms or other input fields in localStorage for pre-filling them on future visits.
  • Implement offline functionality: You can store data locally in localStorage to enable basic functionality even when the user is offline.
  • Track user activity: You can store user activity data in localStorage for analytics purposes.

Limitations of Local Storage

Of course, there are some limitations of uses local stroge, while using it, you should consider the following limitations:

  • Limited Data Types: Only strings can be stored directly, complex objects need serialization.
  • Security Concerns: Data is stored on the user's device and can be accessed by malicious scripts.
  • Cross-domain Access Restrictions: Accessing localStorage from another domain requires special permissions.


localStorage is a powerful tool for JavaScript developers to store data locally in the browser. It offers a simple and efficient way to store information in user's computer.

Thank you for reading.