fix(transducers-hdom): support hdom user context

packages/transducers-hdom/src/index.ts

@@ -8,29 +8,32 @@ import { scan } from "@thi.ng/transducers/xform/scan";
 /**
  * Side-effecting & stateful transducer which receives @thi.ng/hdom
  * component trees, diffs each against previous value and applies
- * required changes to browser DOM starting at given root element. By
- * default, incoming values are first normalized using hdom's
- * `normalizeTree()` function.
+ * required changes to browser DOM starting at given root element.
+ *
+ * By default, incoming values are first normalized using hdom's
+ * `normalizeTree()` function and the given (optional) `ctx` object is
+ * provided to all embedded component functions in the tree.
  *
  * This transducer is primarily intended for @thi.ng/rstream dataflow
  * graph based applications, where this transducer can be used as final
  * leaf subscription to reactively reflect UI changes back to the user,
  * without using the standard RAF update loop used by hdom by default.
- * In this setup, UI updates will only be performed if the stream this
- * transducer is attached too receives new values (i.e. hdom component
+ * In this setup, UI updates will only be performed when the stream this
+ * transducer is attached to emits new values (i.e. hdom component
  * trees).
  *
- * @param el
+ * @param root root element (or ID)
+ * @param ctx hdom user context
  * @param normalize
  */
-export const updateUI = (el: string | Element, normalize = true): Transducer<any, any[]> => {
-    const root = isString(el) ? document.getElementById(el) : el;
+export const updateUI = (root: string | Element, ctx?: any, normalize = true): Transducer<any, any[]> => {
+    root = isString(root) ? document.getElementById(root) : root;
     return scan<any, any[]>(
         reducer(
             () => [],
             (prev, curr) => {
-                normalize && (curr = normalizeTree(curr, {}));
-                diffElement(root, prev, curr);
+                normalize && (curr = normalizeTree(curr, ctx));
+                diffElement(<Element>root, prev, curr);
                 return curr;
             }
         )