A script in the revealing module pattern exposing fn's to create, read, and erase cookies using vanilla JavaScript.

cookie_factory_fns.js

/* --------------------------------------------------------- *\
 *   Vanilla JS Cookie Read/Write/Erase Factory Functions    *
\* --------------------------------------------------------- */


// ES6 Version 
const CookieModule = (() => {

    return {

        createCookie: function(name, value, days) {
            let expires;

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

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

        readCookie: function(name) {
            let nameEQ = name + "=";
            let ca = document.cookie.split(';');

            for (let i = 0; i < ca.length; i++) {
                let 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;
        },

        eraseCookie: function(name) {
            this.createCookie(name, "", -1);
        }
    };
})();



// Legacy JS 
var CookieModule = (function() {

    return {

        createCookie: 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();
            } else {
                expires = "";
            }

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

        readCookie: 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;
        },

        eraseCookie: function(name) {
            this.createCookie(name, "", -1);
        }
    };
})();