First bit of real UI code landed

src/client/initial-app/util.ts

@@ -0,0 +1,15 @@
+/** Creates a function ref that assigns its value to a given property of an object.
+ *  @example
+ *  // element is stored as `this.foo` when rendered.
+ *  <div ref={linkRef(this, 'foo')} />
+ */
+export function linkRef<T>(obj: any, name: string) {
+  const refName = `$$ref_${name}`;
+  let ref = obj[refName];
+  if (!ref) {
+    ref = obj[refName] = (c: T) => {
+      obj[name] = c;
+    };
+  }
+  return ref;
+}