ant-design/components/_util/isFlexSupported.tsx

export default function isFlexSupported() {
  if (typeof window !== 'undefined' && window.document && window.document.documentElement) {
    const { documentElement } = window.document;
    return (
      'flex' in documentElement.style ||
      'webkitFlex' in documentElement.style ||
      'Flex' in documentElement.style ||
      'msFlex' in documentElement.style
    );
  }
  return false;
}