A JavaScript code snippet for logging UTM parameters as a GA4 event, only including parameters that are set in the URL and omitting any parameters that are not set.

ga4-utm-parameters-event.js

// Get the UTM parameters from the URL
var search = window.location.search;
var params = new URLSearchParams(search);

// Keep track of if an event has already been logged
var eventLogged = false;

// Loop through each UTM parameter
for (var [key, value] of params.entries()) {
  // Check if the parameter is "utm_source", "utm_medium", "utm_campaign", "utm_term", or "utm_content"
  if (["utm_source", "utm_medium", "utm_campaign", "utm_term", "utm_content"].indexOf(key) !== -1) {
    // Check if an event has not yet been logged
    if (!eventLogged) {
      // Log the UTM parameters as an event in GA4
      gtag("event", "UTM Parameters", {
        event_category: "UTM",
        event_label: [
          params.get("utm_source") && "utm_source: " + params.get("utm_source"),
          params.get("utm_medium") && "utm_medium: " + params.get("utm_medium"),
          params.get("utm_campaign") && "utm_campaign: " + params.get("utm_campaign"),
          params.get("utm_term") && "utm_term: " + params.get("utm_term"),
          params.get("utm_content") && "utm_content: " + params.get("utm_content")
        ]
        .filter(Boolean)
        .join(", ")
      });

      // Set eventLogged to true so the event is not logged again
      eventLogged = true;
    }
  }
}