Pass UTM params through to dashboard sign-up

utm.js

@@ -0,0 +1,100 @@
+/*
+ * First-touch UTM passthrough to dashboard sign-up.
+ *
+ * Launch posts link straight to docs pages with UTM params, but sign-ups are
+ * tracked on the dashboard, so the params are lost at the hop. Store them on
+ * landing and append them to dashboard links on the way out. kernel/website
+ * writes the same kernel_utm cookie, so the first touch on either site wins.
+ * Mintlify loads every .js file in this directory on every docs page.
+ */
+(function () {
+  var COOKIE_NAME = "kernel_utm";
+  var COOKIE_DOMAIN = "kernel.sh";
+  var MAX_AGE = 60 * 60 * 24 * 30;
+  var DASHBOARD_HOST = "dashboard.onkernel.com";
+  var UTM_KEYS = [
+    "utm_source",
+    "utm_medium",
+    "utm_campaign",
+    "utm_content",
+    "utm_term",
+  ];
+
+  function readStored() {
+    try {
+      var match = document.cookie.match(
+        new RegExp("(?:^|;\\s*)" + COOKIE_NAME + "=([^;]*)")
+      );
+      if (!match) return null;
+      var parsed = JSON.parse(decodeURIComponent(match[1]));
+      return parsed && typeof parsed === "object" ? parsed : null;
+    } catch (e) {
+      return null;
+    }
+  }
+
+  // Shared across www.kernel.sh and the docs. Off kernel.sh (local preview)
+  // the browser would reject the domain, so fall back to a host-only cookie.
+  function cookieAttributes() {
+    var host = location.hostname;
+    var attrs = "; path=/; max-age=" + MAX_AGE + "; SameSite=Lax";
+    if (host === COOKIE_DOMAIN || host.endsWith("." + COOKIE_DOMAIN)) {
+      attrs += "; domain=." + COOKIE_DOMAIN;
+    }
+    if (location.protocol === "https:") attrs += "; Secure";
+    return attrs;
+  }
+
+  function captureFirstTouch() {
+    if (readStored()) return;
+
+    var params = new URLSearchParams(location.search);
+    var utm = {};
+    var found = false;
+    UTM_KEYS.forEach(function (key) {
+      var value = params.get(key);
+      if (value) {
+        utm[key] = value;
+        found = true;
+      }
+    });
+    if (!found) return;
+
+    document.cookie =
+      COOKIE_NAME +
+      "=" +
+      encodeURIComponent(JSON.stringify(utm)) +
+      cookieAttributes();
+  }
+
+  // Delegated so it covers the navbar buttons and links rendered after
+  // client-side navigation. Capture phase rewrites the href before the
+  // browser follows it.
+  function decorate(event) {
+    var link = event.target.closest && event.target.closest("a[href]");
+    if (!link) return;
+
+    var url;
+    try {
+      url = new URL(link.href, location.href);
+    } catch (e) {
+      return;
+    }
+    if (url.hostname !== DASHBOARD_HOST) return;
+
+    var keys = Array.from(url.searchParams.keys());
+    if (keys.some(function (key) { return key.indexOf("utm_") === 0; })) return;
+
+    var utm = readStored();
+    if (!utm) return;
+
+    UTM_KEYS.forEach(function (key) {
+      if (utm[key]) url.searchParams.set(key, utm[key]);
+    });
+    link.href = url.toString();
+  }
+
+  captureFirstTouch();
+  document.addEventListener("click", decorate, { capture: true });
+  document.addEventListener("auxclick", decorate, { capture: true });
+})();