feat: allow to render function components

src/lib/YarJS.ts

@@ -124,6 +124,14 @@ function updateDom(
     });
 }
 
+function commitDeletion(fiber: YarFiber, domParent: HTMLElement | Text) {
+  if (fiber.dom) {
+    domParent.removeChild(fiber.dom);
+  } else {
+    commitDeletion(fiber.child!, domParent);
+  }
+}
+
 /**
  * Actually commit the processed Fiber to the real DOM
  * @param fiber - The Fiber Element to process
@@ -131,14 +139,23 @@ function updateDom(
 function commitWork(fiber: YarFiber | null) {
   if (!fiber) return;
 
-  const domParent = fiber.parent!.dom!;
+  // we can have fibers without dom nodes,
+  // so we search for the first parent with one
+  let parentFiber = fiber.parent!;
+  while (!parentFiber.dom) {
+    parentFiber = parentFiber.parent!;
+  }
+
+  const domParent = parentFiber.dom!;
 
   switch (fiber.effectTag) {
     case YarEffectTag.Placement:
-      domParent.appendChild(fiber.dom!);
+      if (fiber.dom) {
+        domParent.appendChild(fiber.dom);
+      }
       break;
     case YarEffectTag.Deletion:
-      domParent.removeChild(fiber.dom!);
+      commitDeletion(fiber, domParent);
       break;
     case YarEffectTag.Update:
       updateDom(fiber.dom!, fiber.alternate!.props, fiber.props);
@@ -159,6 +176,26 @@ function commitRoot() {
   WIP_ROOT = null;
 }
 
+function updateFunctionComponent(fiber: YarFiber) {
+  // the fiber from a function component doesn’t have a DOM node
+  // and the children come from running the function instead of getting them directly from the props
+
+  if (!(fiber.type instanceof Function)) return;
+
+  const children = [fiber.type(fiber.props)];
+  reconcileChildren(fiber, children);
+}
+
+function updateNativeComponent(fiber: YarFiber) {
+  if (!fiber.dom) {
+    // Create the actual dom element
+    fiber.dom = generateDomNode(fiber);
+  }
+
+  // Create a new fiber for each child
+  reconcileChildren(fiber, fiber.props.children);
+}
+
 /**
  * Process the Fiber Tree, this is a representation of the DOM
  * Since this process could be interrupted before the whole
@@ -168,14 +205,12 @@ function commitRoot() {
  * @param fiber - The Fiber to process
  */
 function processFiber(fiber: YarFiber): YarFiber | undefined {
-  if (!fiber.dom) {
-    // Create the actual dom element
-    fiber.dom = generateDomNode(fiber);
+  if (fiber.type instanceof Function) {
+    updateFunctionComponent(fiber);
+  } else {
+    updateNativeComponent(fiber);
   }
 
-  // Create a new fiber for each child
-  reconcileChildren(fiber, fiber.props.children);
-
   // Search for the new fiber that needs to be processed
   if (fiber.child) {
     // return the first child of the current fiber

src/lib/YarJs.interfaces.ts

@@ -1,4 +1,7 @@
-export type YarHTMLTagName = keyof React.JSX.IntrinsicElements | string;
+export type YarHTMLTagName =
+  | keyof React.JSX.IntrinsicElements
+  | string
+  | Function;
 
 export enum YarEffectTag {
   Update,

src/main.tsx

@@ -3,19 +3,9 @@ import { render } from "./lib/YarJS";
 
 const root = document.querySelector<HTMLDivElement>("#app")!;
 
-const rerender = (value: string) => {
-  const onChange = (e: React.FormEvent<HTMLInputElement>) => {
-    rerender(e.currentTarget.value);
-  };
-
-  const element = (
-    <div id="foo">
-      <input type="text" onInput={onChange} value={value} />
-      <h2>Hello {value}</h2>
-    </div>
-  );
+function App(props) {
+  return <h1>Hi {props.name}</h1>;
+}
 
+const element = <App name="foo" />;
 render(element, root);
-};
-
-rerender("foo");