5   const iframe = document.createElement('iframe');
6   document.body.appendChild(iframe);
7   return iframe;
11   const iframe = addIframe();  constant
12   const stream = new iframe.contentWindow.TextDecoderStream();
16   iframe.remove();
21   const iframe = addIframe();  constant
22   const stream = new iframe.contentWindow.TextEncoderStream();
26   iframe.remove();
32     const iframe = addIframe();  constant
33     const stream = new iframe.contentWindow[type]();
34     iframe.remove();