To track events with Google Tag (gtag.js) on a site with GA4, you need to have a basic understanding of JavaScript and familiarity with the gtag.js library. Here's a step-by-step guide:

1. Ensure gtag.js is installed: Verify that gtag.js is installed on your site and that you have the correct measurement ID from your GA4 data stream.
2. Review Google Tag developer documentation: Familiarize yourself with the gtag() function and its commands, focusing on the event command for sending event data to GA4.
3. Create an event: Write JavaScript code to listen for user interactions, such as clicks, and use the gtag('event', '<event_name>', {<event_parameters>}) syntax to send event data to GA4.
4. Test the event: Use the Google Analytics Debugger Chrome extension and Debugview in GA4 to test and ensure that your events are being tracked correctly.

Remember to follow the recommended naming convention for event names and parameters, and be aware of event limits, such as the maximum number of characters for event names and parameters.

The prerequisites for tracking events with gtag.js include:

• gtag.js installed on your site: You must have gtag.js installed on your site, which is the native tracking code library for platforms like GA4 or Google Ads.
• Familiarity with JavaScript: A solid understanding of JavaScript is required to track events using gtag.js. If you're not familiar with JavaScript, you may need to work with a developer.

Before starting, you should also review the Google Tag developer documentation to understand the different commands you can use within the gtag() function.

To find the measurement ID for your GA4 data stream, follow these steps:

1. Log in to your GA4 interface.
2. Go to Admin.
3. Navigate to Data collection and modification > Data streams.
4. Click on the data stream you are interested in.
5. Locate the measurement ID within the data stream details.

The measurement ID is essential for configuring gtag.js on your site.

To create a dynamic event tracking code for link clicks using gtag.js, you'll need to write JavaScript code that captures click events and sends them to GA4 with relevant parameters. Here's an example code snippet:

<script>
document.addEventListener("click", function(event) {
 if (event.target.tagName === "A") {
 gtag('event', 'link_click', {
 'link_text': event.target.innerText,
 'link_url': event.target.href,
 'link_id': event.target.id,
 'link_classes': event.target.className
 });
 }
});
</script>

This code listens for click events and, if the click is on a link (<a> tag), it sends an event to GA4 with the name 'link_click' and parameters such as link_text, link_url, link_id, and link_classes. These parameters are dynamic and will change based on the specific link clicked by the user.