A simple utm link passthrough

utm_track.js

(function() {
  // Helper function to get UTM parameters from the URL
  function getUTMParams() {
    const urlParams = new URLSearchParams(window.location.search);
    const utmParams = {};
    ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content'].forEach(param => {
      if (urlParams.has(param)) {
        utmParams[param] = urlParams.get(param);
      }
    });
    return utmParams;
  }

  // Helper function to append UTM parameters to a given URL
  function appendUTMParamsToUrl(url, utmParams) {
    if (Object.keys(utmParams).length === 0) return url; // If no UTM params, return original URL

    const urlObj = new URL(url);
    Object.keys(utmParams).forEach(key => {
      urlObj.searchParams.set(key, utmParams[key]);
    });
    return urlObj.toString();
  }

  // Main function to modify the hrefs of specific links
  function appendUTMToLinks(targetUrl) {
    const utmParams = getUTMParams();
    if (Object.keys(utmParams).length === 0) return; // Do nothing if no UTM params exist

    const links = document.querySelectorAll(`a[href^="${targetUrl}"]`);
    links.forEach(link => {
      link.href = appendUTMParamsToUrl(link.href, utmParams);
    });
  }

  // Example: Modify all links that point to "https://example.com"
  const targetBaseUrl = "https://example.com"; // Change this to your target URL
  appendUTMToLinks(targetBaseUrl);

  // Optional: Automatically run this on all clicks on the page
  document.body.addEventListener('click', function(event) {
    const target = event.target.closest('a');
    if (target && target.href.startsWith(targetBaseUrl)) {
      target.href = appendUTMParamsToUrl(target.href, getUTMParams());
    }
  });
})();