Web Storage in JavaScript

Web Storage, can store data locally within the user's browser.

1) Check Browser Support

Before using web storage, check browser support for localStorage and sessionStorage:

if (typeof(Storage) !== "undefined") {
  // Code for localStorage/sessionStorage.
} else {
  // Sorry! No Web Storage support..
}

2) To Store Data

Create a localStorage name/value pair with name="fname" and value="Steve"

localStorage.setItem("fname", "Steve");

OR

localStorage.fname = "Steve";

3) To Retrieve Data

Retrieve the value of "fname" and insert it into the element with id="result"

localStorage.getItem("fname");

OR

localStorage.fname;

4) Remove Storage Item

To remove the "fname" localStorage item

localStorage.removeItem("fname");

OR

delete localStorage.fname;

5) Clearing Storage

To Clear (delete) all stored data

localStorage.clear();

6) To Store Structured Data

To store structured data, you can use JSON to serialize it to and from strings for storage

var students = [{name: "Tyler", marks: 22}, {name: "Ryan", marks: 41}];
localStorage.setItem('students', JSON.stringify(students));
console.log(JSON.parse(localStorage.getItem('students')));
// [ Object { name: "Tyler", marks: 22 }, Object { name: "Ryan", marks: 41 } ]

7) Session Storage

The sessionStorage object implements the same Storage interface as localStorage. However, instead of being
shared with all pages from the same origin, sessionStorage data is stored separately for every window/tab.

• Save data to sessionStorage

sessionStorage.setItem('key', 'value');

• Get saved data from sessionStorage

var data = sessionStorage.getItem('key');

• Remove saved data from sessionStorage

sessionStorage.removeItem('key')

8) Error Condition

When browsers are set to prevent cookies, they often block localStorage as well. This will lead to exception if you try to use it. Remember to handle these situations accordingly.

var video = document.querySelector('video')
try {
 video.volume = localStorage.getItem('volume')
} catch (error) {
 alert('If you\'d like your volume saved, turn on cookies')
}
video.play()

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