Manipulating Storage Data

Data saved in Web Storage is stored as key/value pairs.

A few examples of simple key/value pairs:
■ key: name, value: Fernando
■ key: painter, value: David
■ key: email, value: info@rookienerd.com

Setting the data

(I) sessionStorage
To store some data for only the current browser instance (goes away when the user closes the browser), use sessionStorage

snippet

var user_id = "A1B2C3D4";
var user_data = {
    name: "Tom Hanks",
    occupation: "Actor",
    favorite_color: "Blue"
        // ...
};
sessionStorage.setItem(user_id, JSON.stringify(user_data));

(II) localStorage
To store some data for a longer period of time, use localStorage

snippet

var user_id = "A1B2C3D4";
var user_prefs = {
    keep_me_logged_in: true,
    start_page: "daily news"
        // ...
};
localStorage.setItem(user_id, JSON.stringify(user_prefs));

Shortcut Way:-
Instead of localStorage.setItem(key, value), we can say localStorage[key]= value: localStorage["size"] = 6;

localStorage.setItem(key, value)

[or]

localStorage[key]= value

Getting the data

To pull data from the storage container:

snippet

var user_id = "A1B2C3D4";
var user_data = { /* defaults */ };
var user_prefs = { /* defaults */ };
if (sessionStorage.getItem(user_id)) {
    user_data = JSON.parse(sessionStorage.getItem(user_id));
}
if (localStorage.getItem(user_id)) {
    user_prefs = JSON.parse(localStorage.getItem(user_id));
}

These Storage APIs allow you to very simply set and retrieve key/value data, where the value is a string, but can represent anything you want, including the string serialization of a complex data object.

Shortcut Way:-
Instead of localStorage.getItem(key), we can simply say localStorage[key].

var size = localStorage["size"];

Removing Items and Clearing Data

Method	Description
`removeItem(key)`	To remove a specific item from Web Storage, we can use the removeItem method. We pass it the key we want to remove, and it will remove both the key and its value.
`clear()`	To remove all data stored by our site on a user's computer, we can use the clear method. This will delete all keys and all values stored for our domain.