How do I set/unset a cookie with jQuery?

Here is my global module I use -

var Cookie = {   

   Create: function (name, value, days) {

       var expires = "";

        if (days) {
           var date = new Date();
           date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
           expires = "; expires=" + date.toGMTString();
       }

       document.cookie = name + "=" + value + expires + "; path=/";
   },

   Read: function (name) {

        var nameEQ = name + "=";
        var ca = document.cookie.split(";");

        for (var i = 0; i < ca.length; i++) {
            var c = ca[i];
            while (c.charAt(0) == " ") c = c.substring(1, c.length);
            if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length, c.length);
        }

        return null;
    },

    Erase: function (name) {

        Cookie.create(name, "", -1);
    }

};

Reducing the number of operations compared to previous answers, I use the following.

function setCookie(name, value, expiry) {
    let d = new Date();
    d.setTime(d.getTime() + (expiry*86400000));
    document.cookie = name + "=" + value + ";" + "expires=" + d.toUTCString() + ";path=/";
}

function getCookie(name) {
    let cookie = document.cookie.match('(^|;) ?' + name + '=([^;]*)(;|$)');
    return cookie ? cookie[2] : null;
}

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

I thought Vignesh Pichamani's answer was the simplest and cleanest. Just adding to his the ability to set the number of days before expiration:

EDIT: also added 'never expires' option if no day number is set

        function setCookie(key, value, days) {
            var expires = new Date();
            if (days) {
                expires.setTime(expires.getTime() + (days * 24 * 60 * 60 * 1000));
                document.cookie = key + '=' + value + ';expires=' + expires.toUTCString();
            } else {
                document.cookie = key + '=' + value + ';expires=Fri, 30 Dec 9999 23:59:59 GMT;';
            }
        }

        function getCookie(key) {
            var keyValue = document.cookie.match('(^|;) ?' + key + '=([^;]*)(;|$)');
            return keyValue ? keyValue[2] : null;
        }

Set the cookie:

setCookie('myData', 1, 30); // myData=1 for 30 days. 
setCookie('myData', 1); // myData=1 'forever' (until the year 9999) 

I know there are many great answers. Often, I only need to read cookies and I do not want to create overhead by loading additional libraries or defining functions.

Here is how to read cookies in one line of javascript. I found the answer in Guilherme Rodrigues' blog article:

('; '+document.cookie).split('; '+key+'=').pop().split(';').shift()

This reads the cookie named key, nice, clean and simple.

Try (doc here, SO snippet not works so run this one)

document.cookie = "test=1"             // set
document.cookie = "test=1;max-age=0"   // unset

The following code will remove all cookies within the current domain and all trailing subdomains (www.some.sub.domain.com, .some.sub.domain.com, .sub.domain.com and so on.).

A single line vanilla JS version (no need for jQuery):

document.cookie.replace(/(?<=^|;).+?(?=\=|;|$)/g, name => location.hostname.split('.').reverse().reduce(domain => (domain=domain.replace(/^\.?[^.]+/, ''),document.cookie=`${name}=;max-age=0;path=/;domain=${domain}`,domain), location.hostname));

This is a readable version of this single line:

document.cookie.replace(
  /(?<=^|;).+?(?=\=|;|$)/g, 
  name => location.hostname
    .split(/\.(?=[^\.]+\.)/)
    .reduceRight((acc, val, i, arr) => i ? arr[i]='.'+val+acc : (arr[i]='', arr), '')
    .map(domain => document.cookie=`${name}=;max-age=0;path=/;domain=${domain}`)
);

I know, there are plenty of answers already, but here's one that has set, get, and delete all beautifully vanilla and nicely put into a global reference:

window.cookieMonster = window.cookieMonster || 
    {
        // https://stackoverflow.com/a/25490531/1028230
        get: function (cookieName) {
            var b = document.cookie.match('(^|;)\\s*' + cookieName + '\\s*=\\s*([^;]+)');
            return b ? b.pop() : '';
        },

        delete: function (name) {
            document.cookie = '{0}=; Path=/; Expires=Thu, 01 Jan 1970 00:00:01 GMT;'
                .replace('{0}', name);
        },

        set: function (name, value) {
            document.cookie =
                '{0}={1};expires=Fri, 31 Dec 9999 23:59:59 GMT;path=/;SameSite=Lax'
                .replace('{0}', name)
                .replace('{1}', value);
        }
    };

Notice cookie getting regex was taken from this answer to a question in another castle.

And let's test:

cookieMonster.set('chocolate', 'yes please');
cookieMonster.set('sugar', 'that too');

console.log(cookieMonster.get('chocolate'));
console.log(document.cookie);

cookieMonster.delete('chocolate');

console.log(cookieMonster.get('chocolate'));
console.log(document.cookie);

If you didn't have any cookies before trying, should give you...

yes please
chocolate=yes please; sugar=that too

sugar=that too

Notice the cookies last not quite heat-death-of-the-universe long, but essentially that from our perspective. You can figure out how to change dates pretty easily from looking at the strings here or from other answers.

How to use it?

//To set a cookie
$.cookie('the_cookie', 'the_value');

//Create expiring cookie, 7 days from then:
$.cookie('the_cookie', 'the_value', { expires: 7 });

//Create expiring cookie, valid across entire page:
$.cookie('the_cookie', 'the_value', { expires: 7, path: '/' });

//Read cookie
$.cookie('the_cookie'); // => 'the_value'
$.cookie('not_existing'); // => null

//Delete cookie by passing null as value:
$.cookie('the_cookie', null);

// Creating cookie with all availabl options
$.cookie('myCookie2', 'myValue2', { expires: 7, path: '/', domain: 'example.com', 
         secure: true, raw: true });

Available Options:

expires: Define lifetime of the cookie. Value can be a Number (which will be interpreted as days from time of creation) or a Date object. If omitted, the cookie is a session cookie.

path: Define the path where cookie is valid. By default the path of the cookie is the path of the page where the cookie was created (standard browser behavior). If you want to make it available for instance across the entire page use path: '/'.

domain: Domain of page where the cookie was created.

secure: Default: false. If true, the cookie transmission requires a secure protocol (https).

raw: By default the cookie is encoded/decoded when creating/reading, using encodeURIComponent/ decodeURIComponent. Turn off by setting raw: true.