diff --git a/node_modules/.package-lock.json b/node_modules/.package-lock.json
index c02c3ed..a6e4de5 100644
--- a/node_modules/.package-lock.json
+++ b/node_modules/.package-lock.json
@@ -952,6 +952,19 @@
       "integrity": "sha512-Y/arvbn+rrz3JCKl9C4kVNfTfSm2/mEp5FSz5EsZSANGPSlQrpRI5M4PKF+mJnE52jOO90PnPSc3Ur3bTQw0gA==",
       "dev": true
     },
+    "node_modules/typescript": {
+      "version": "6.0.3",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-6.0.3.tgz",
+      "integrity": "sha512-y2TvuxSZPDyQakkFRPZHKFm+KKVqIisdg9/CZwm9ftvKXLP8NRWj38/ODjNbr43SsoXqNuAisEf1GdCxqWcdBw==",
+      "dev": true,
+      "bin": {
+        "tsc": "bin/tsc",
+        "tsserver": "bin/tsserver"
+      },
+      "engines": {
+        "node": ">=14.17"
+      }
+    },
     "node_modules/util-deprecate": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/util-deprecate/-/util-deprecate-1.0.2.tgz",
diff --git a/package-lock.json b/package-lock.json
index 0d02bf3..7d8399c 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -8,7 +8,8 @@
       "devDependencies": {
         "htm": "^3.1.1",
         "preact": "^10.29.2",
-        "tailwindcss": "^3.4.17"
+        "tailwindcss": "^3.4.17",
+        "typescript": "^6.0.3"
       }
     },
     "node_modules/@alloc/quick-lru": {
@@ -960,6 +961,19 @@
       "integrity": "sha512-Y/arvbn+rrz3JCKl9C4kVNfTfSm2/mEp5FSz5EsZSANGPSlQrpRI5M4PKF+mJnE52jOO90PnPSc3Ur3bTQw0gA==",
       "dev": true
     },
+    "node_modules/typescript": {
+      "version": "6.0.3",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-6.0.3.tgz",
+      "integrity": "sha512-y2TvuxSZPDyQakkFRPZHKFm+KKVqIisdg9/CZwm9ftvKXLP8NRWj38/ODjNbr43SsoXqNuAisEf1GdCxqWcdBw==",
+      "dev": true,
+      "bin": {
+        "tsc": "bin/tsc",
+        "tsserver": "bin/tsserver"
+      },
+      "engines": {
+        "node": ">=14.17"
+      }
+    },
     "node_modules/util-deprecate": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/util-deprecate/-/util-deprecate-1.0.2.tgz",
diff --git a/package.json b/package.json
index 7b263b4..210a1a1 100644
--- a/package.json
+++ b/package.json
@@ -8,6 +8,7 @@
   "devDependencies": {
     "htm": "^3.1.1",
     "preact": "^10.29.2",
-    "tailwindcss": "^3.4.17"
+    "tailwindcss": "^3.4.17",
+    "typescript": "^6.0.3"
   }
 }
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..668cc8b
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,21 @@
+{
+  "compilerOptions": {
+    "checkJs": true,
+    "allowJs": true,
+    "noEmit": true,
+    "strict": true,
+    "lib": ["dom", "es2022"],
+    "target": "es2022",
+    "module": "es2022",
+    "moduleResolution": "bundler",
+    "paths": {
+      "https://esm.sh/preact@10": ["./node_modules/preact/src/index.d.ts"],
+      "https://esm.sh/preact@10/hooks": ["./node_modules/preact/hooks/src/index.d.ts"],
+      "https://esm.sh/htm@3/preact": ["./node_modules/htm/preact/index.d.ts"]
+    }
+  },
+  "include": [
+    "web/modules/custom/riverside_pt/js/**/*.js",
+    "web/modules/custom/riverside_pt/js/globals.d.ts"
+  ]
+}
diff --git a/web/modules/custom/riverside_pt/js/components/rpt-appt-type.js b/web/modules/custom/riverside_pt/js/components/rpt-appt-type.js
index 8c693d2..27fd45b 100644
--- a/web/modules/custom/riverside_pt/js/components/rpt-appt-type.js
+++ b/web/modules/custom/riverside_pt/js/components/rpt-appt-type.js
@@ -16,6 +16,7 @@ const CHECK = html`<svg width="14" height="11" viewBox="0 0 14 11" fill="none" x
 function ApptType() {
   const [selected, setSelected] = useState("diagnostic");
 
+  /** @param {string} id */
   function select(id) {
     setSelected(id);
     document.dispatchEvent(new CustomEvent("rpt:appt-type-change", { detail: { type: id } }));
diff --git a/web/modules/custom/riverside_pt/js/components/rpt-booking.js b/web/modules/custom/riverside_pt/js/components/rpt-booking.js
index 55708e4..fcc515a 100644
--- a/web/modules/custom/riverside_pt/js/components/rpt-booking.js
+++ b/web/modules/custom/riverside_pt/js/components/rpt-booking.js
@@ -15,6 +15,7 @@ const CHECK = html`<svg width="14" height="11" viewBox="0 0 14 11" fill="none" x
 
 const EMPTY_FORM = { firstName: "", lastName: "", email: "", phone: "", comments: "" };
 
+/** @param {string | number} [raw] */
 function formatPhone(raw) {
   let d = String(raw || "").replace(/\D/g, "");
   if (d.length === 11 && d[0] === "1") {
@@ -70,6 +71,7 @@ const CX = {
   successNote:    "text-sm text-green-700",
 };
 
+/** @param {Date} d */
 function localDateStr(d) {
   return d.getFullYear() + "-" +
     String(d.getMonth() + 1).padStart(2, "0") + "-" +
@@ -83,12 +85,14 @@ function nextBusinessDay() {
   return localDateStr(d);
 }
 
+/** @param {string} startStr */
 function slotLabel(startStr) {
   var d = new Date(startStr);
   var h = d.getHours();
   return (h % 12 || 12) + (h < 12 ? "AM" : "PM") + " PST";
 }
 
+/** @param {string} startStr */
 function formatAppointmentDate(startStr) {
   var parts = startStr.split("T")[0].split("-");
   var d = new Date(parseInt(parts[0]), parseInt(parts[1]) - 1, parseInt(parts[2]));
@@ -100,32 +104,35 @@ function formatAppointmentDate(startStr) {
 // Keyed by service in the parent, so it always mounts fresh for each service.
 // service is a prop here — it never changes within an instance's lifetime,
 // which means the fetch effect can depend only on dateRange (no stale-service risk).
+/**
+ * @param {{ service: string, settings: RiversidePtSettings }} props
+ */
 function BookingPanel({ service, settings }) {
-  const [dateRange, setDateRange] = useState(null);
-  const [fetchedEvents, setFetchedEvents] = useState(null);
+  const [dateRange, setDateRange] = useState(/** @type {string | null} */ (null));
+  const [fetchedEvents, setFetchedEvents] = useState(/** @type {RiversidePtEvent[] | null} */ (null));
   const [fetchLoading, setFetchLoading] = useState(false);
-  const [slots, setSlots] = useState([]);
-  const [selectedSlotId, setSelectedSlotId] = useState(null);
+  const [slots, setSlots] = useState(/** @type {RiversidePtEvent[]} */ ([]));
+  const [selectedSlotId, setSelectedSlotId] = useState(/** @type {number | string | null} */ (null));
   const [formData, setFormData] = useState(EMPTY_FORM);
   const [submitting, setSubmitting] = useState(false);
-  const [submitError, setSubmitError] = useState(null);
+  const [submitError, setSubmitError] = useState(/** @type {string | null} */ (null));
   const [success, setSuccess] = useState(false);
-  const [confirmedAppointment, setConfirmedAppointment] = useState(null);
+  const [confirmedAppointment, setConfirmedAppointment] = useState(/** @type {{ start: string, service: string, firstName: string, lastName: string, email: string } | null} */ (null));
   const [noSlotsInMonth, setNoSlotsInMonth] = useState(false);
 
-  const calEl = useRef(null);
-  const calRef = useRef(null);
+  const calEl = useRef(/** @type {HTMLDivElement | null} */ (null));
+  const calRef = useRef(/** @type {any} */ (null));
   const initializedRef = useRef(false);
   const autoAdvanceRef = useRef(0);
-  const fetchAbortRef = useRef(null);
+  const fetchAbortRef = useRef(/** @type {AbortController | null} */ (null));
   // Instance-scoped vars for FullCalendar callbacks (no stale-closure risk via .current).
-  const selectedDateRef = useRef(null);
-  const selectedDateSlotsRef = useRef([]);
-  const currentEventsRef = useRef([]);
+  const selectedDateRef = useRef(/** @type {string | null} */ (null));
+  const selectedDateSlotsRef = useRef(/** @type {RiversidePtEvent[]} */ ([]));
+  const currentEventsRef = useRef(/** @type {RiversidePtEvent[]} */ ([]));
   const initDate = useMemo(nextBusinessDay, []);
-  const formRef = useRef(null);
-  const prevSlotIdRef = useRef(null);
-  const successRef = useRef(null);
+  const formRef = useRef(/** @type {HTMLFormElement | null} */ (null));
+  const prevSlotIdRef = useRef(/** @type {number | string | null} */ (null));
+  const successRef = useRef(/** @type {HTMLDivElement | null} */ (null));
 
   function buildEventsUrl() {
     return settings.eventsUrl + "?service=" + service;
@@ -133,15 +140,19 @@ function BookingPanel({ service, settings }) {
 
   // ── Initialize FullCalendar once ─────────────────────────────────────
   useEffect(function () {
-    if (!calEl.current || !window.FullCalendar) return;
+    var root = calEl.current;
+    if (!root || !window.FullCalendar) return;
+    /** @type {HTMLDivElement} */
+    var rootEl = root;
 
-    var cal = new FullCalendar.Calendar(calEl.current, {
+    var FC = window.FullCalendar || FullCalendar;
+    var cal = new FC.Calendar(root, {
       initialView: "dayGridMonth",
       initialDate: initDate,
       headerToolbar: { left: "prev", center: "title", right: "next" },
       titleFormat: { year: "numeric", month: "long" },
       dayHeaderFormat: { weekday: "narrow" },
-      validRange: function (now) {
+      validRange: function (/** @type {any} */ now) {
         return {
           start: new Date(now.getFullYear(), now.getMonth(), 1),
           end: new Date(now.getFullYear(), now.getMonth() + 7, 1),
@@ -153,14 +164,14 @@ function BookingPanel({ service, settings }) {
       eventDisplay: "none",
       dayMaxEvents: false,
 
-      datesSet: function (info) {
-        calEl.current.querySelectorAll(".fc-daygrid-day.is-selected").forEach(function (d) {
+      datesSet: function (/** @type {any} */ info) {
+        rootEl.querySelectorAll(".fc-daygrid-day.is-selected").forEach(function (/** @type {any} */ d) {
           d.classList.remove("is-selected");
         });
         setSelectedSlotId(null);
         setNoSlotsInMonth(false);
         if (selectedDateRef.current) {
-          var dayEl = calEl.current.querySelector(".fc-daygrid-day[data-date=\"" + selectedDateRef.current + "\"]");
+          var dayEl = rootEl.querySelector(".fc-daygrid-day[data-date=\"" + selectedDateRef.current + "\"]");
           if (dayEl) {
             dayEl.classList.add("is-selected");
             setSlots(selectedDateSlotsRef.current);
@@ -173,31 +184,31 @@ function BookingPanel({ service, settings }) {
         setDateRange(info.startStr + "/" + info.endStr);
       },
 
-      eventsSet: function (events) {
-        calEl.current.querySelectorAll(".fc-daygrid-day.has-availability").forEach(function (d) {
+      eventsSet: function (/** @type {any[]} */ events) {
+        rootEl.querySelectorAll(".fc-daygrid-day.has-availability").forEach(function (/** @type {any} */ d) {
           d.classList.remove("has-availability");
         });
-        events.forEach(function (event) {
+        events.forEach(function (/** @type {any} */ event) {
           var dateStr = event.startStr.substring(0, 10);
-          var dayEl = calEl.current.querySelector(".fc-daygrid-day[data-date=\"" + dateStr + "\"]");
+          var dayEl = rootEl.querySelector(".fc-daygrid-day[data-date=\"" + dateStr + "\"]");
           if (dayEl) dayEl.classList.add("has-availability");
         });
       },
 
-      dayCellClassNames: function (arg) {
+      dayCellClassNames: function (/** @type {any} */ arg) {
         var date = arg.date.toISOString().substring(0, 10);
         if (settings.holidays[date]) return ["is-holiday"];
       },
 
-      dateClick: function (arg) {
+      dateClick: function (/** @type {any} */ arg) {
         if (!arg.dayEl.classList.contains("has-availability")) return;
-        calEl.current.querySelectorAll(".fc-daygrid-day.is-selected").forEach(function (d) {
+        rootEl.querySelectorAll(".fc-daygrid-day.is-selected").forEach(function (/** @type {any} */ d) {
           d.classList.remove("is-selected");
         });
         arg.dayEl.classList.add("is-selected");
         var daySlots = currentEventsRef.current
-          .filter(function (e) { return e.start.startsWith(arg.dateStr); })
-          .sort(function (a, b) { return a.start < b.start ? -1 : 1; });
+          .filter(function (/** @type {RiversidePtEvent} */ e) { return e.start.startsWith(arg.dateStr); })
+          .sort(function (/** @type {RiversidePtEvent} */ a, /** @type {RiversidePtEvent} */ b) { return a.start < b.start ? -1 : 1; });
         selectedDateRef.current = arg.dateStr;
         selectedDateSlotsRef.current = daySlots;
         setSelectedSlotId(null);
@@ -229,12 +240,12 @@ function BookingPanel({ service, settings }) {
     setFetchedEvents(null);
     fetch(url, { signal: controller.signal })
       .then(function (r) { return r.json(); })
-      .then(function (data) {
+      .then(function (/** @type {RiversidePtEvent[]} */ data) {
         currentEventsRef.current = data;
         setFetchedEvents(data);
         setFetchLoading(false);
       })
-      .catch(function (err) {
+      .catch(function (/** @type {any} */ err) {
         if (err.name === "AbortError") return;
         currentEventsRef.current = [];
         setFetchedEvents([]);
@@ -254,15 +265,16 @@ function BookingPanel({ service, settings }) {
       cal.addEventSource(fetchedEvents);
 
       if (!initializedRef.current) {
-        var dates = [...new Set(fetchedEvents.map(function (e) { return e.start.substring(0, 10); }))].sort();
+        var dates = [...new Set(fetchedEvents.map(function (/** @type {RiversidePtEvent} */ e) { return e.start.substring(0, 10); }))].sort();
         var firstDate = dates[0];
         if (firstDate) {
           var firstSlots = fetchedEvents
-            .filter(function (e) { return e.start.startsWith(firstDate); })
-            .sort(function (a, b) { return a.start < b.start ? -1 : 1; });
+            .filter(function (/** @type {RiversidePtEvent} */ e) { return e.start.startsWith(firstDate); })
+            .sort(function (/** @type {RiversidePtEvent} */ a, /** @type {RiversidePtEvent} */ b) { return a.start < b.start ? -1 : 1; });
           selectedDateRef.current = firstDate;
           selectedDateSlotsRef.current = firstSlots;
-          var targetEl = calEl.current.querySelector(".fc-daygrid-day[data-date=\"" + firstDate + "\"]");
+          var root = calEl.current;
+          var targetEl = root ? root.querySelector(".fc-daygrid-day[data-date=\"" + firstDate + "\"]") : null;
           if (targetEl) {
             initializedRef.current = true;
             autoAdvanceRef.current = 0;
@@ -292,28 +304,34 @@ function BookingPanel({ service, settings }) {
     }
   }, [success]);
 
+  /** @param {RiversidePtEvent} slot */
   function handleSlotClick(slot) {
     setSelectedSlotId(slot.id);
     setSubmitError(null);
     setSuccess(false);
   }
 
+  /** @param {string} field @param {string} value */
   function handleFormChange(field, value) {
     setFormData(function (prev) { return Object.assign({}, prev, { [field]: value }); });
   }
 
+  /** @param {Event} e */
   function handleSubmit(e) {
     e.preventDefault();
-    var slot = slots.find(function (s) { return s.id === selectedSlotId; });
+    var slot = slots.find(function (/** @type {RiversidePtEvent} */ s) { return s.id === selectedSlotId; });
     if (!slot) return;
+    // Capture values synchronously; the async callbacks close over these, not the find result.
+    var chosenStart = slot.start;
+    var chosenEnd = slot.end;
     setSubmitting(true);
     setSubmitError(null);
     fetch(settings.storeSlotUrl, {
       method: "POST",
       headers: { "Content-Type": "application/json" },
       body: JSON.stringify({
-        start: slot.start,
-        end: slot.end,
+        start: chosenStart,
+        end: chosenEnd,
         service: service,
         firstName: formData.firstName,
         lastName: formData.lastName,
@@ -326,7 +344,7 @@ function BookingPanel({ service, settings }) {
         setSubmitting(false);
         setSubmitError(null);
         setConfirmedAppointment({
-          start: slot.start,
+          start: chosenStart,
           service: service,
           firstName: formData.firstName,
           lastName: formData.lastName,
@@ -340,7 +358,7 @@ function BookingPanel({ service, settings }) {
         if (res.status === 422) {
           setSubmitError("That slot was just booked. Please choose another time.");
         } else {
-          res.json().then(function (data) {
+          res.json().then(function (/** @type {{message?: string}} */ data) {
             setSubmitError(data.message || "Something went wrong. Please try again.");
           }).catch(function () {
             setSubmitError("Something went wrong. Please try again.");
@@ -353,7 +371,7 @@ function BookingPanel({ service, settings }) {
     });
   }
 
-  var selectedSlot = slots.find(function (s) { return s.id === selectedSlotId; });
+  var selectedSlot = slots.find(function (/** @type {RiversidePtEvent} */ s) { return s.id === selectedSlotId; });
 
   return html`
     <div>
@@ -372,11 +390,11 @@ function BookingPanel({ service, settings }) {
         ${slots.length > 0 ? html`
           <div id="riverside-slots-wrap">
             <p class="text-xs text-gray-500 mb-3">Select a time on ${(function () {
-              var p = slots[0].start.split("T")[0].split("-");
+              var p = slots[0] ? slots[0].start.split("T")[0].split("-") : ["","",""];
               return parseInt(p[1]) + "/" + parseInt(p[2]) + "/" + p[0];
             })()}:</p>
             <div id="riverside-booking-slots">
-              ${slots.map(function (slot) {
+              ${slots.map(function (/** @type {RiversidePtEvent} */ slot) {
                 return html`
                   <button
                     key=${slot.id}
@@ -407,7 +425,7 @@ function BookingPanel({ service, settings }) {
                 autocomplete="given-name"
                 required
                 value=${formData.firstName}
-                onInput=${function (e) { handleFormChange("firstName", e.target.value); }}
+                onInput=${function (/** @type {any} */ e) { handleFormChange("firstName", e.target.value); }}
                 class=${CX.formInput}
               />
             </div>
@@ -422,7 +440,7 @@ function BookingPanel({ service, settings }) {
                 autocomplete="family-name"
                 required
                 value=${formData.lastName}
-                onInput=${function (e) { handleFormChange("lastName", e.target.value); }}
+                onInput=${function (/** @type {any} */ e) { handleFormChange("lastName", e.target.value); }}
                 class=${CX.formInput}
               />
             </div>
@@ -437,7 +455,7 @@ function BookingPanel({ service, settings }) {
                 autocomplete="email"
                 required
                 value=${formData.email}
-                onInput=${function (e) { handleFormChange("email", e.target.value); }}
+                onInput=${function (/** @type {any} */ e) { handleFormChange("email", e.target.value); }}
                 class=${CX.formInput}
               />
             </div>
@@ -452,7 +470,7 @@ function BookingPanel({ service, settings }) {
                 autocomplete="tel"
                 required
                 value=${formatPhone(formData.phone)}
-                onInput=${function (e) {
+                onInput=${function (/** @type {any} */ e) {
                   handleFormChange("phone", formatPhone(e.target.value));
                 }}
                 class=${CX.formInput}
@@ -470,7 +488,7 @@ function BookingPanel({ service, settings }) {
               name="comments"
               autocomplete="off"
               value=${formData.comments}
-              onInput=${function (e) { handleFormChange("comments", e.target.value); }}
+              onInput=${function (/** @type {any} */ e) { handleFormChange("comments", e.target.value); }}
               class=${CX.formTextarea}
             ></textarea>
           </div>
@@ -491,7 +509,7 @@ function BookingPanel({ service, settings }) {
             <div class=${CX.successSummary}>
               <p>${confirmedAppointment.firstName} ${confirmedAppointment.lastName}</p>
               <p>${confirmedAppointment.email}</p>
-              <p>${TYPES.find(function (t) { return t.id === confirmedAppointment.service; }).label}</p>
+              <p>${(TYPES.find(function (/** @type {{id:string,label:string}} */ t) { return t.id === confirmedAppointment.service; }) || {}).label}</p>
               <p>${formatAppointmentDate(confirmedAppointment.start)}</p>
             </div>
             <p class=${CX.successNote}>We'll contact you shortly to confirm your appointment.</p>
@@ -506,8 +524,11 @@ function BookingPanel({ service, settings }) {
 // Owns service selection and the type selector UI. Keys BookingPanel by
 // service so it mounts fresh on every change — no reset effects, no races.
 // Starts with null so no service is pre-selected.
+/**
+ * @param {{ settings: RiversidePtSettings }} props
+ */
 function Booking({ settings }) {
-  const [service, setService] = useState(null);
+  const [service, setService] = useState(/** @type {string | null} */ (null));
 
   return html`
     <div style="min-height:460px">
@@ -519,7 +540,7 @@ function Booking({ settings }) {
             <button
               key=${t.id}
               onClick=${function () {
-                setService(t.id);
+                setService(/** @type {string} */ (t.id));
               }}
               style="text-align:left; cursor:pointer;"
               class=${CX.typeBtn + " " + (active ? CX.typeBtnActive : CX.typeBtnInactive)}
@@ -548,7 +569,8 @@ function Booking({ settings }) {
 
 class RptBooking extends HTMLElement {
   connectedCallback() {
-    render(html`<${Booking} settings=${window.drupalSettings.riversidePt} />`, this);
+    var settings = (window.drupalSettings && window.drupalSettings.riversidePt) || /** @type {RiversidePtSettings} */ ({ eventsUrl: "", storeSlotUrl: "", holidays: {} });
+    render(html`<${Booking} settings=${settings} />`, this);
   }
   disconnectedCallback() {
     render(null, this);
diff --git a/web/modules/custom/riverside_pt/js/components/rpt-carousel.js b/web/modules/custom/riverside_pt/js/components/rpt-carousel.js
index 72ad366..74d4aa8 100644
--- a/web/modules/custom/riverside_pt/js/components/rpt-carousel.js
+++ b/web/modules/custom/riverside_pt/js/components/rpt-carousel.js
@@ -12,7 +12,7 @@ const IMAGES = [
 function Carousel() {
   const [index, setIndex] = useState(0);
   const [itemWidth, setItemWidth] = useState(0);
-  const containerRef = useRef(null);
+  const containerRef = useRef(/** @type {HTMLDivElement | null} */ (null));
 
   useLayoutEffect(() => {
     const update = () => {
diff --git a/web/modules/custom/riverside_pt/js/components/rpt-faq.js b/web/modules/custom/riverside_pt/js/components/rpt-faq.js
index 43a4930..b02d124 100644
--- a/web/modules/custom/riverside_pt/js/components/rpt-faq.js
+++ b/web/modules/custom/riverside_pt/js/components/rpt-faq.js
@@ -29,6 +29,9 @@ const FAQS = [
   },
 ];
 
+/**
+ * @param {{ item: {q: string, a: string}, open: boolean, onToggle: () => void }} props
+ */
 function FaqItem({ item, open, onToggle }) {
   return html`
     <div class="border-b border-gray-200">
@@ -50,9 +53,9 @@ function FaqItem({ item, open, onToggle }) {
 }
 
 function Faq() {
-  const [openIndex, setOpenIndex] = useState(null);
+  const [openIndex, setOpenIndex] = useState(/** @type {number | null} */ (null));
 
-  const toggle = function(i) {
+  const toggle = function(/** @type {number} */ i) {
     setOpenIndex(function(prev) { return prev === i ? null : i; });
   };
 
diff --git a/web/modules/custom/riverside_pt/js/components/rpt-testimonials.js b/web/modules/custom/riverside_pt/js/components/rpt-testimonials.js
index 0bd85a9..e97a1fc 100644
--- a/web/modules/custom/riverside_pt/js/components/rpt-testimonials.js
+++ b/web/modules/custom/riverside_pt/js/components/rpt-testimonials.js
@@ -35,10 +35,10 @@ const STEP = CARD_W + GAP;
 const TOTAL_W = TESTIMONIALS.length * CARD_W + (TESTIMONIALS.length - 1) * GAP;
 
 function Testimonials() {
-  const containerRef = useRef(null);
-  const trackRef = useRef(null);
+  const containerRef = useRef(/** @type {HTMLDivElement | null} */ (null));
+  const trackRef = useRef(/** @type {HTMLDivElement | null} */ (null));
   const [left, setLeft] = useState(0);
-  const [, forceUpdate] = useReducer(function (n) { return n + 1; }, 0);
+  const [, forceUpdate] = useReducer(/** @type {(n: number, action?: any) => number} */ (function (n) { return n + 1; }), 0);
 
   function measureMax() {
     if (!containerRef.current) return 0;
@@ -55,13 +55,14 @@ function Testimonials() {
   };
 
   useEffect(function () {
+    /** @type {number | undefined} */
     var timer;
     function onResize() {
       clearTimeout(timer);
       timer = setTimeout(function () {
         var max = measureMax();
         setLeft(function (l) { return Math.min(0, Math.max(-max, l)); });
-        forceUpdate();
+        forceUpdate(0);
       }, 150);
     }
     window.addEventListener("resize", onResize);
@@ -71,23 +72,26 @@ function Testimonials() {
     };
   }, []);
 
-  var drag = useRef(null); // null when idle, {x, left} when dragging
+  var drag = useRef(/** @type {{x: number, left: number} | null} */ (null)); // null when idle, {x, left} when dragging
 
+  /** @param {PointerEvent} e */
   var onPointerDown = function (e) {
     drag.current = { x: e.clientX, left: left };
-    trackRef.current.style.transition = "none";
-    e.currentTarget.setPointerCapture(e.pointerId);
+    if (trackRef.current) trackRef.current.style.transition = "none";
+    if (e.currentTarget instanceof Element) e.currentTarget.setPointerCapture(e.pointerId);
   };
 
+  /** @param {PointerEvent} e */
   var onPointerMove = function (e) {
     if (!drag.current) return;
     setLeft(drag.current.left + (e.clientX - drag.current.x));
   };
 
+  /** @param {PointerEvent} e */
   var onPointerUp = function (e) {
     if (!drag.current) return;
     drag.current = null;
-    trackRef.current.style.transition = "left 0.5s ease";
+    if (trackRef.current) trackRef.current.style.transition = "left 0.5s ease";
     var max = measureMax();
     setLeft(function (l) {
       var clamped = Math.min(0, Math.max(-max, l));
diff --git a/web/modules/custom/riverside_pt/js/globals.d.ts b/web/modules/custom/riverside_pt/js/globals.d.ts
index aa8df3a..7e15ab1 100644
--- a/web/modules/custom/riverside_pt/js/globals.d.ts
+++ b/web/modules/custom/riverside_pt/js/globals.d.ts
@@ -1,14 +1,25 @@
 interface RiversidePtSettings {
   eventsUrl: string;
   storeSlotUrl: string;
-  bookingUrl: string;
+  bookingUrl?: string;
   holidays: Record<string, boolean>;
   scrollTo?: string;
 }
 
+interface RiversidePtEvent {
+  id: number | string;
+  title?: string;
+  start: string;
+  end: string;
+  startStr?: string;
+}
+
 interface Window {
+  FullCalendar?: any;
   rptScrollTo: (el: Element, animate?: boolean) => void;
   drupalSettings?: {
     riversidePt?: RiversidePtSettings;
   };
 }
+
+declare const FullCalendar: any;
diff --git a/web/modules/custom/riverside_pt/js/nav.js b/web/modules/custom/riverside_pt/js/nav.js
index 70447b6..050a4f7 100644
--- a/web/modules/custom/riverside_pt/js/nav.js
+++ b/web/modules/custom/riverside_pt/js/nav.js
@@ -2,8 +2,8 @@
   'use strict';
 
   document.addEventListener('DOMContentLoaded', function () {
-    var btn = document.querySelector('.rpt-header__hamburger');
-    var nav = document.getElementById('rpt-main-nav');
+    const btn = document.querySelector('.rpt-header__hamburger');
+    const nav = document.getElementById('rpt-main-nav');
     if (!btn || !nav) return;
 
     btn.addEventListener('click', function () {
@@ -20,7 +20,7 @@
     });
 
     document.addEventListener('click', function (e) {
-      if (!e.target.closest('.rpt-header')) {
+      if (!(e.target instanceof Element) || !e.target.closest('.rpt-header')) {
         nav.classList.remove('is-open');
         btn.setAttribute('aria-expanded', 'false');
       }
diff --git a/web/modules/custom/riverside_pt/js/phone-format.js b/web/modules/custom/riverside_pt/js/phone-format.js
index 64027e0..8c58cc6 100644
--- a/web/modules/custom/riverside_pt/js/phone-format.js
+++ b/web/modules/custom/riverside_pt/js/phone-format.js
@@ -1,4 +1,5 @@
 (function () {
+  /** @param {unknown} raw */
   function formatPhone(raw) {
     let d = String(raw || "").replace(/\D/g, "");
     if (d.length === 11 && d[0] === "1") {
@@ -13,6 +14,7 @@
     return "(" + d.slice(0, 3) + ") " + d.slice(3, 6) + "-" + d.slice(6);
   }
 
+  /** @param {HTMLInputElement} input */
   function enhancePhoneInput(input) {
     if (input.dataset.phoneEnhanced) return;
     input.dataset.phoneEnhanced = "true";
@@ -55,7 +57,7 @@
   }
 
   function scan() {
-    document.querySelectorAll("input.rpt-phone").forEach(enhancePhoneInput);
+    /** @type {NodeListOf<HTMLInputElement>} */ (document.querySelectorAll("input.rpt-phone")).forEach(enhancePhoneInput);
   }
 
   if (document.readyState === "loading") {
diff --git a/web/modules/custom/riverside_pt/js/scroll.js b/web/modules/custom/riverside_pt/js/scroll.js
index 5e6c731..c890ae0 100644
--- a/web/modules/custom/riverside_pt/js/scroll.js
+++ b/web/modules/custom/riverside_pt/js/scroll.js
@@ -4,7 +4,7 @@ var FIXED_BUFFER = 0; // breathing room below fixed header when menu is closed
 // When the hamburger is open, offsetHeight already includes the expanded nav,
 // so no extra buffer is needed. When closed, add FIXED_BUFFER for breathing room.
 function headerOffset() {
-  var header = document.querySelector(".rpt-header");
+  var header = /** @type {HTMLElement | null} */ (document.querySelector(".rpt-header"));
   if (!header) return 0;
   var pos = window.getComputedStyle(header).position;
   if (pos !== "fixed" && pos !== "sticky") return 0;
@@ -13,6 +13,7 @@ function headerOffset() {
   return header.offsetHeight + (menuOpen ? 0 : FIXED_BUFFER);
 }
 
+/** @param {Element} el @param {boolean} [animate] */
 function scrollToEl(el, animate) {
   var top = Math.max(0, el.getBoundingClientRect().top + window.scrollY - headerOffset());
   window.scrollTo({ top: top, behavior: animate ? "smooth" : "instant" });
@@ -26,7 +27,7 @@ document.addEventListener("DOMContentLoaded", function () {
   var settings = window.drupalSettings && window.drupalSettings.riversidePt;
   var anchor = window.location.hash || (settings && settings.scrollTo);
   if (!anchor) return;
-  var target = document.querySelector(anchor);
+  const target = document.querySelector(anchor);
   if (!target) return;
   requestAnimationFrame(function () {
     scrollToEl(target, false);
@@ -34,9 +35,10 @@ document.addEventListener("DOMContentLoaded", function () {
 });
 
 document.addEventListener("click", function (e) {
-  var link = e.target.closest("[data-scroll-to]");
+  if (!(e.target instanceof Element)) return;
+  var link = /** @type {HTMLElement | null} */ (e.target.closest("[data-scroll-to]"));
   if (!link) return;
-  var target = document.querySelector(link.dataset.scrollTo);
+  var target = document.querySelector(link.dataset.scrollTo || "");
   if (!target) return;
   e.preventDefault();
   history.pushState({}, "", link.getAttribute("href"));