JavaScript LocalStorage

The complete guide to using localStorage in JavaScript apps

LocalStorage is a type of web storage that allows Javascript websites and apps to store and access data right in the browser with no expiration date. This means the data stored in the browser will persist even after the browser window has been closed.

LocalStorage in JavaScript: How to

To use localStorage in your web applications, there are five methods to choose from:

1. setItem(): Add key and value to localStorage
2. getItem(): Retrieve a value by the key from localStorage
3. removeItem(): Remove an item by key from localStorage
4. clear(): Clear all localStorage
5. key(): Passed a number to retrieve nth key of a localStorage

setItem()

This method just as the name implies allows you to store values in the localStorage object.

It takes two parameters, a key and a value. The key can be referenced later to fetch the value attached to it.

window.localStorage.setItem('name', 'Obaseki Nosa');

Where name is the key and Obaseki Nosa is the value. Also note that localStorage can only store strings.

To store arrays or objects you would have to convert them to strings.

To do this we use the JSON.stringify() method before passing to setItem().

const person = {
  name: "Obaseki Nosa",
  location: "Lagos",
}

window.localStorage.setItem('user', JSON.stringify(person));

getItem()

The getItem() method allows you to access the data stored in the browser’s localStorage object.

It accepts only one parameter which is the key and returns the value as a string.

To retrieve the user key stored above:

window.localStorage.getItem('user');

This returns a string with value as;

“{“name”:”Obaseki Nosa”,”location”:”Lagos”}”

To use this value, you would have convert it back to an object.

To do this, we make use of JSON.parse() method which converts a JSON string into a Javascript Object.

JSON.parse(window.localStorage.getItem('user'));

removeItem()

The removeItem() method when passed a key name, will remove that key from the storage if it exists. If there is no item associated with the given key, this method will do nothing.

window.localStorage.removeItem('name');

clear()

This method, when invoked clears the entire storage of all records for that domain. It does not receive any parameters.

window.localStorage.clear();

key()

The key() method comes in handy in situations where you need to loop through keys and allows you pass a number or index to local storage to retrieve the name of the key.

var KeyName = window.localStorage.key(index);

LocalStorage JavaScript browser support

LocalStorage as a type of web storage is an HTML5 specification. It is supported by major browsers including IE8. To be sure the browser supports localStorage, you can check using the following snippet:

if (typeof(Storage) !== "undefined") {
   // Code for localStorage
} else {
   // No web storage Support.
}