Iframe ContentWindow document cross-origin error

I was coding with JavaScript and then I met a problem.

I use the iframe.contentWindow.document; to get the Iframe document but I got an error.

Here is the code

   /**
   *
   * @param {HTMLIFrameElement} iframe
   */
  function getIframeElements(iframe) {
    const iframeDocumentElements = iframe.contentWindow.document;
    console.log(iframeDocumentElements);
  }

The error :