feat: add dead click detection to tracking script

public/script.js

@@ -547,6 +547,127 @@
     }, true); // * Capture phase
   }
 
+  // * Auto-track dead clicks (clicks on interactive elements that produce no effect)
+  // * Fires dead_click when an interactive element is clicked but no DOM change, navigation,
+  // * or network request occurs within 1 second
+  // * Opt-out: add data-no-dead to the script tag
+  if (!script.getAttribute('data-no-dead')) {
+    var INTERACTIVE_SELECTOR = 'a,button,input,select,textarea,[role="button"],[role="link"],[role="tab"],[role="menuitem"],[onclick],[tabindex]';
+    var DEAD_CLICK_DEBOUNCE = 10000;
+    var DEAD_CLEANUP_INTERVAL = 30000;
+    var deadClickDebounce = {}; // * selector -> lastFiredTimestamp
+
+    // * Cleanup stale dead click debounce entries every 30 seconds
+    setInterval(function() {
+      var now = Date.now();
+      for (var key in deadClickDebounce) {
+        if (!deadClickDebounce.hasOwnProperty(key)) continue;
+        if (now - deadClickDebounce[key] > DEAD_CLEANUP_INTERVAL) {
+          delete deadClickDebounce[key];
+        }
+      }
+    }, DEAD_CLEANUP_INTERVAL);
+
+    // * Polyfill check for Element.matches
+    var matchesFn = (function() {
+      var ep = Element.prototype;
+      return ep.matches || ep.msMatchesSelector || ep.webkitMatchesSelector || null;
+    })();
+
+    // * Find the nearest interactive element by walking up max 3 levels
+    function findInteractiveElement(el) {
+      if (!matchesFn) return null;
+      var depth = 0;
+      var current = el;
+      while (current && depth <= 3) {
+        if (current.nodeType === 1 && matchesFn.call(current, INTERACTIVE_SELECTOR)) {
+          return current;
+        }
+        current = current.parentElement;
+        depth++;
+      }
+      return null;
+    }
+
+    document.addEventListener('click', function(e) {
+      var target = findInteractiveElement(e.target);
+      if (!target) return;
+
+      var selector = getElementIdentifier(target);
+      if (!selector) return;
+
+      var now = Date.now();
+
+      // * Debounce: max one dead_click per element per 10 seconds
+      if (deadClickDebounce[selector] && now - deadClickDebounce[selector] < DEAD_CLICK_DEBOUNCE) {
+        return;
+      }
+
+      var currentPath = window.location.pathname + window.location.search;
+      var clickX = String(Math.round(e.clientX));
+      var clickY = String(Math.round(e.clientY));
+      var effectDetected = false;
+      var hrefBefore = location.href;
+      var mutationObs = null;
+      var perfObs = null;
+      var cleanupTimer = null;
+
+      function cleanup() {
+        if (mutationObs) { try { mutationObs.disconnect(); } catch (ex) {} mutationObs = null; }
+        if (perfObs) { try { perfObs.disconnect(); } catch (ex) {} perfObs = null; }
+        if (cleanupTimer) { clearTimeout(cleanupTimer); cleanupTimer = null; }
+      }
+
+      function onEffect() {
+        effectDetected = true;
+        cleanup();
+      }
+
+      // * Set up MutationObserver to detect DOM changes on the element and its parent
+      if (typeof MutationObserver !== 'undefined') {
+        try {
+          mutationObs = new MutationObserver(function() {
+            onEffect();
+          });
+          var mutOpts = { childList: true, attributes: true, characterData: true, subtree: true };
+          mutationObs.observe(target, mutOpts);
+          if (target.parentElement) {
+            mutationObs.observe(target.parentElement, mutOpts);
+          }
+        } catch (ex) {
+          mutationObs = null;
+        }
+      }
+
+      // * Set up PerformanceObserver to detect network requests
+      if (typeof PerformanceObserver !== 'undefined') {
+        try {
+          perfObs = new PerformanceObserver(function() {
+            onEffect();
+          });
+          perfObs.observe({ type: 'resource' });
+        } catch (ex) {
+          perfObs = null;
+        }
+      }
+
+      // * After 1 second, check if any effect was detected
+      cleanupTimer = setTimeout(function() {
+        cleanup();
+        // * Also check if navigation occurred
+        if (effectDetected || location.href !== hrefBefore) return;
+
+        deadClickDebounce[selector] = Date.now();
+        trackCustomEvent('dead_click', {
+          selector: selector,
+          page_path: currentPath,
+          x: clickX,
+          y: clickY
+        });
+      }, 1000);
+    }, true); // * Capture phase
+  }
+
   // * Auto-track outbound link clicks and file downloads (on by default)
   // * Opt-out: add data-no-outbound or data-no-downloads to the script tag
   var trackOutbound = !script.hasAttribute('data-no-outbound');