Function render

packages/react-dom/src/client/ReactDOMRootFB.js:388–433

(
  element: React$Element<any>,
  container: Container,
  callback: ?Function,
)

}

export function render(
  element: React$Element<any>,
  container: Container,
  callback: ?Function,
): component(...props: any) | PublicInstance | null {
  if (disableLegacyMode) {
    if (__DEV__) {
      console.error(
        'ReactDOM.render was removed in React 19. Use createRoot instead.',
      );
    }
    throw new Error('ReactDOM: Unsupported Legacy Mode API.');
  }
  if (__DEV__) {
    console.error(
      'ReactDOM.render has not been supported since React 18. Use createRoot ' +
        'instead. Until you switch to the new API, your app will behave as ' +
        "if it's running React 17. Learn " +
        'more: https://react.dev/link/switch-to-createroot',
    );
  }

  if (!isValidContainer(container)) {
    throw new Error('Target container is not a DOM element.');
  }

  if (__DEV__) {
    const isModernRoot =
      isContainerMarkedAsRoot(container) &&
      container._reactRootContainer === undefined;
    if (isModernRoot) {
      console.error(
        'You are calling ReactDOM.render() on a container that was previously ' +
          'passed to ReactDOMClient.createRoot(). This is not supported. ' +
          'Did you mean to call root.render(element)?',
      );
    }
  }
  return legacyRenderSubtreeIntoContainer(
    null,
    element,
    container,
    false,
    callback,
  );
}

export function unmountComponentAtNode(container: Container): boolean {
  if (disableLegacyMode) {