function createExternalScript(
  src: string,
  onLoadCallback?: () => any | null
): HTMLScriptElement {
  const externalScript = document.createElement('script');
  externalScript.setAttribute('type', 'text/javascript');
  externalScript.setAttribute('language', 'javascript');
  externalScript.setAttribute('src', src);
  externalScript.onload = () => {
    if (!!onLoadCallback) {
      onLoadCallback();
    }
  };
  return externalScript;
}

export default function insertExternalScript(
  src: string,
  rootElement: HTMLElement | null,
  onLoadCallback?: () => any | null
): HTMLScriptElement {
  const externalScript = createExternalScript(src, onLoadCallback);

  if (!!rootElement) {
    rootElement.insertAdjacentElement('afterend', externalScript);
  }

  return externalScript;
}