Cookie-based user tracking for heatmaps in JavaScript

24 Sep 2023

Heatmaps are a powerful tool for analyzing user behavior on a website. They provide visual representations of where users are focusing their attention, which can be valuable for optimizing web design and layout. One challenge in implementing heatmaps is accurately tracking individual users as they navigate through different pages on a website. One approach to achieve this is by using cookie-based user tracking in JavaScript.

In this blog post, we will explore how to implement cookie-based user tracking specifically for the purpose of generating heatmaps using JavaScript. We will cover the following steps:

Setting up the cookie
Updating the cookie on page load
Sending the cookie data to a heatmap service

To start implementing cookie-based user tracking, we need to create a cookie that will store the user’s unique identifier. This identifier is used to track the user’s activity across multiple pages. Here’s an example of how to set a cookie using JavaScript:

function setCookie(name, value, days) {
  const expires = new Date();
  expires.setTime(expires.getTime() + (days * 24 * 60 * 60 * 1000));
  document.cookie = `${name}=${value};expires=${expires.toUTCString()};path=/`;
}

const userId = 'unique_user_id'; // Replace with your own logic to generate a unique identifier for each user
setCookie('user_id', userId, 365); // Set the cookie with an expiration of 365 days

In the code above, we define a function setCookie that takes three arguments: the cookie name, the value to be stored in the cookie, and the number of days until the cookie expires. We then call setCookie with the name 'user_id', the generated userId, and an expiration of 365 days.

To track the user’s activity, we need to update the cookie every time a page is loaded. This ensures that the cookie always contains the most recent information about the user. Here’s an example of updating the cookie on page load:

document.addEventListener('DOMContentLoaded', () => {
  const userId = getCookieValue('user_id'); // Retrieve the user ID from the cookie
  // Replace this with your own code to send the user ID to a heatmap service
});

function getCookieValue(name) {
  const cookies = document.cookie.split(';');
  for (let i = 0; i < cookies.length; i++) {
    const cookie = cookies[i].trim();
    if (cookie.startsWith(`${name}=`)) {
      return cookie.substring(name.length + 1);
    }
  }
  return null;
}

In the above code, we use the getCookieValue function to retrieve the user ID from the cookie. We then have the opportunity to send this user ID to a heatmap service, which we will discuss in the next section.

To generate heatmaps, the cookie data needs to be sent to a heatmap service that can analyze and visualize the user’s behavior on the website. There are various heatmap services available that can handle this. One popular service is Hotjar. Here’s an example of how to send the user ID to Hotjar:

document.addEventListener('DOMContentLoaded', () => {
  const userId = getCookieValue('user_id'); // Retrieve the user ID from the cookie
  if (userId) {
    window.hj('identify', userId); // Send the user ID to Hotjar
  }
});

In the code above, we check if the user ID exists and then use the window.hj function provided by Hotjar to send the user ID to the service.

By setting up the cookie, updating it on page load, and sending the cookie data to a heatmap service, we can effectively track individual users for heatmaps using JavaScript. This information can then be used for data-driven decision making in improving website design and optimizing user experience.

#heatmap #webanalytics

Setting up the cookie

Updating the cookie on page load

Sending the cookie data to a heatmap service