add focus tool; time input: refactor away from bind:ref

src/lib/util.ts

@@ -69,3 +69,21 @@ export const getValue = (option: Option): string => {
 		return option.value;
 	}
 };
+
+/**
+ * targetMust returns the target of an event coerced to a particular type and
+ * throws an error if the target does not exist or is not connected.
+ *
+ * @returns The target element coerced to a particular type.
+ * @throws Will throw an error if the target is null or not connected to the DOM.
+ */
+export function targetMust<T extends HTMLElement>(event: Event): T {
+	const target = event.target as T | null;
+	if (!target) {
+		throw new Error('Event target is null');
+	}
+	if (!target.isConnected) {
+		throw new Error('Event target is not connected to the DOM');
+	}
+	return target;
+}