Expanding attributes of JSX element

enhanceJSXAttributes.d.ts

/// <reference path="../node_modules/@types/react/index.d.ts" />

/**
 * Enhancer of JSX attributes
 */
type EnhanceAttributes<
  Tagname extends keyof React.ReactHTML,
  NewAttributes extends {},
  T = React.ReactHTML[Tagname]
> = T extends React.DetailedHTMLFactory<infer A, infer E>
  ? React.DetailedHTMLProps<A, E> & NewAttributes
  : null;

/**
 * Expanding attributes of JSX <table> element for example
 */
declare namespace JSX {
  interface IntrinsicElements {
    table: EnhanceAttributes<
      'table',
      { border?: number; bgcolor?: string; width?: string }
    >;
  }
}