What are JavaScript Cookies?

Cookies are data, stored in small text files , on your computer. Web Browsers and Servers use HTTP protocol to communicate and HTTP is a stateless protocol . When a web server has sent a web page to a browser, the connection is shut down, and the server forgets everything about the user. But for a commercial website, it is required to maintain session information among different pages. In order for it to remember users information, cookies are used. Cookies are stored in the computer in name-value pairs.
username = Bill Gates
In JavaScript, use the "document.cookie" property to create, delete and read cookies., but the interface provided by this object is very primitive.

Create Cookie

document.cookie = "username=Bill Gates";

Add an expiry date (in UTC time)

document.cookie = "username=Bill Gates; expires=Fri, 20 Dec 2014 12:00:00 UTC";

With a path parameter, you can tell the browser what path the cookie belongs to. By default, the cookie belongs to the current page.

document.cookie = "username=Bill Gates; expires=Fri, 20 Dec 2014 12:00:00 UTC; path=/";

Read a Cookie

var ck = document.cookie;

Change a Cookie

Changing cookies in JavaScript is the same as creating them. The old cookie’s value is deleted.

document.cookie = "username=Bill Gates; expires=Fri, 20 Dec 2022 12:00:00 UTC; path=/";

Delete a Cookie

document.cookie = "username=; expires=Fri, 20 Dec 2014 12:00:00 UTC; path=/;";

Functions to Get, Set and Delete Cookie in JavaScript.

Set Cookie

function setCookie(cookName, cookValue, expiry) { var dt = new Date(); dt.setTime(dt.getTime() + (expiry*24*60*60*1000)); var expires = "expires="+ dt.toUTCString(); document.cookie = cookName + "=" + cookValue + ";" + expiry + ";path=/"; }

Get Cookie

function getCookie(cookName) { var cname = cookName + "="; var deCookie = decodeURIComponent(document.cookie); var cookArray = decodedCookie.split(';'); for(var i = 0; i <cookArray.length; i++) { var c = cookArray; while (c.charAt(0) == ' ') { c = c.substring(1); } if (c.indexOf(cname) == 0) { return c.substring(cname.length, c.length); } } return ""; }

Delete Cookie

function deleteCookie(name){ setCookie(name,"",-1); }