Setting and reading a custom cookie

This page describes how to work with cookies in a light module, especially how to read, set and remove them. The page concludes the whole tutorial by providing instructions to create a page template and bits of JavaScript code for component personalization through the visits cookie.

Manipulating cookies with JavaScript

Normally cookie manipulations can be done with the default JavaScript API as described here. However, they can be accomplished more easily by using the JavaScript Cookie library, which we will apply in the code provided further below for cookie manipulations in a FreeMarker page template.

The JavaScript Cookie library

JavaScript Cookie, hereinafter referred to as js-cookie, is a lightweight JavaScript API designed specifically for handling browser cookies.

Availability

The library is available:

From the js-cookie repository on GitHub. To use the library in a light module, download the js.cookie.js file from the repository and add it to your light module.
In the travel-demo-theme and hence in any Magnolia bundle containing the magnolia-travel-demo module. You could simply attach this theme to your template to use the library’s functions in your light module. However, if your project is to be completely independent from this theme, you will need a copy of the library from GitHub and provide it in your light module.

Handling cookies in the library

Handling cookies via this library is simple. To read, set or remove a cookie named foo, for example, just the following commands need to be called from a JavaScript code attached to a web page:

Cookies.get('foo');
Cookies.set('foo', 'value');
Cookies.remove('foo');

See the usage section in the library’s repository for a full list of commands defined for cookie manipulations.

Creating a page template for manipulating cookies

In the following steps we will create page template files and a JavaScript file for manipulating the visits cookie, and provide all of the files in a light module called visits-cookie-365. You can also download the files from the cookie-trait-examples repository.

Create a light module

Create the following light module structure in the directory defined by the magnolia.resources.dir property:

visits-cookie-365/
├── templates/
│ └── pages/
└── webresources/
    ├── css/
    └── js/

Add the js.cookie.js file to the js subfolder of the module. The css subfolder together with its content will influence mainly the visual aspect of the page.

Create JavaScript code for manipulating cookies

Remember that in our use case, we want a cookie to count the number of times a user visits a web page. The counting will be done by the following JavaScript code, while reading, removing and setting a cookie will be done via calls to the js-cookie library from the code:

function setVisitsCookie() {
    var visitsCookie = isNaN(Cookies.get('visits')) ? 1 : parseInt(Cookies.get('visits')) + 1;
    Cookies.remove('visits');
    Cookies.set('visits', visitsCookie, { expires: 365 });
}

This code will:

on line 2: Check whether the visits cookie has been stored in the browser.
- If not or its value is an illegal number, it will assign 1 as the value of the visitsCookie variable.
- If yes, it will take the integer value of the visits cookie, increment it by 1, and assign it as the value of the visitsCookie variable.
on line 3: Remove the visits cookie so as not to end up with two visits cookies after executing the next step.
on line 4: Create the visits cookie and use the value kept in the visitsCookie variable as the value of the cookie. Define that the cookie should expire in 365 days. This will make sure that the cookie will be kept in the browser not just for the duration of the current session. The value 365 has been chosen arbitrarily.

Save this function as the visits.js file to the js subfolder in the module.

Create a page template

Create a page template with a template definition and a template script. To keep things simple, we will not add any dialog definition to the template.

The template definition

cookiePage.yaml

https://git.magnolia-cms.com/projects/DOCUMENTATION/repos/cookie-trait-examples/raw/light-modules/visits-cookie-365/templates/pages/cookiePage.yaml?at=master

This template defines an area in the page that may contain the textImage component. The component will be used to create content variants. Add this template definition as the cookiePage.yaml file to the pages subfolder in the module.

The template script

Add the following template script as the cookiePage.ftl file to the pages subfolder in the module:

cookiePage.ftl

https://git.magnolia-cms.com/projects/DOCUMENTATION/repos/cookie-trait-examples/raw/light-modules/visits-cookie-365/templates/pages/cookiePage.ftl?at=master

line 9: Includes the js-cookie library.
line 10: Includes the custom JavaScript with the counting function for the visits cookie.
line 14: The #setVisitsCookie function is called every time the page is loaded using the onload attribute of the body tag.
line 21: The cms.area directive will render the components of this area.

which will allow you to test component personalization based on cookie values. :smile:

Use the module to create pages with a personalized component

Use the light module on a running Magnolia instance. Go to the Pages app and create a page with the template called Visits cookie 365.

Add page dialog

Add a textImage component to the page and personalize it, i.e. create several variants of it defined by the custom visits cookie trait. The following screenshot, for example, shows a message for a variant called VISITS1.

Variants of textImage component

Publish your page and check the result. The screenshot below shows page content for any value > 4 of the visits cookie, as set in the website.Cookie-Test-Page.xml page configuration file available in the cookie-trait-examples repository:

Published page