[IMP] env: env is now frozen, useSubEnv does not affect user env

src/hooks.ts

@@ -0,0 +1,41 @@
+import type { Env } from "./app/app";
+import { getCurrent } from "./component/component_node";
+
+// -----------------------------------------------------------------------------
+// useRef
+// -----------------------------------------------------------------------------
+
+/**
+ * The purpose of this hook is to allow components to get a reference to a sub
+ * html node or component.
+ */
+export function useRef<T extends HTMLElement = HTMLElement>(name: string): { el: T | null } {
+  const node = getCurrent()!;
+  return {
+    get el(): T | null {
+      return node.refs[name] || null;
+    },
+  };
+}
+
+// -----------------------------------------------------------------------------
+// useEnv and useSubEnv
+// -----------------------------------------------------------------------------
+
+/**
+ * This hook is useful as a building block for some customized hooks, that may
+ * need a reference to the env of the component calling them.
+ */
+export function useEnv<E extends Env>(): E {
+  return getCurrent()!.component.env as any;
+}
+
+/**
+ * This hook is a simple way to let components use a sub environment.  Note that
+ * like for all hooks, it is important that this is only called in the
+ * constructor method.
+ */
+export function useSubEnv(envExtension: Env) {
+  const node = getCurrent()!;
+  node.childEnv = Object.freeze(Object.assign({}, node.childEnv, envExtension));
+}