Function findDOMNode

packages/react-dom/src/client/ReactDOMRootFB.js:356–386

(
  componentOrElement: Element | ?component(...props: any),
)

}

export function findDOMNode(
  componentOrElement: Element | ?component(...props: any),
): null | Element | Text {
  if (__DEV__) {
    const owner = currentOwner;
    if (owner !== null && isRendering && owner.stateNode !== null) {
      const warnedAboutRefsInRender = owner.stateNode._warnedAboutRefsInRender;
      if (!warnedAboutRefsInRender) {
        console.error(
          '%s is accessing findDOMNode inside its render(). ' +
            'render() should be a pure function of props and state. It should ' +
            'never access something that requires stale data from the previous ' +
            'render, such as refs. Move this logic to componentDidMount and ' +
            'componentDidUpdate instead.',
          getComponentNameFromType(owner.type) || 'A component',
        );
      }
      owner.stateNode._warnedAboutRefsInRender = true;
    }
  }
  if (componentOrElement == null) {
    return null;
  }
  if ((componentOrElement: any).nodeType === ELEMENT_NODE) {
    return (componentOrElement: any);
  }
  if (__DEV__) {
    return findHostInstanceWithWarning(componentOrElement, 'findDOMNode');
  }
  return findHostInstance(componentOrElement);
}

export function render(
  element: React$Element<any>,