Add renderer helper - types and is check functions

src/helpers.ts

@@ -0,0 +1,40 @@
+import {
+  ElementType,
+  FunctionComponent,
+  ComponentClass,
+  PropsWithChildren,
+  ReactText
+} from "react";
+
+export type ReactElementSubset<TProps = {}> = {
+  props: PropsWithChildren<TProps>;
+  type: ElementType<TProps>;
+};
+
+export type ReactElementSubsetWithPrimitive =
+  | ReactElementSubset
+  | ReactText
+  | Array<ReactElementSubsetWithPrimitive>
+  | null
+  | undefined;
+
+export function isFunctionalComponent(
+  eleType: ElementType
+): eleType is FunctionComponent {
+  return (
+    typeof eleType === "function" && // can be various things
+    !(
+      (eleType.prototype && eleType.prototype.isReactComponent) // native arrows don't have prototypes // special property
+    )
+  );
+}
+
+export function isClassComponent(
+  eleType: ElementType
+): eleType is ComponentClass {
+  return !!(
+    typeof eleType === "function" &&
+    eleType.prototype &&
+    eleType.prototype.isReactComponent
+  );
+}