How to render to a placeholder when sing renderAsync

When Rendering via jsreport.render(placeholder, request) works fine. Because of the time it takes for some reports to render we would like to put up a spinner and remove it when finished. The only way I can see to do this is using the jsreport.renderAsync(request) using the promise when returned to stop the spinner. This seems to work fine, but how do I now use the response and render it to the placeholder?

It is a phantom pdf template being rendered by the way.

<div ref='placeholder' id='placeholder'></div>

// old way works good
jsreport.render(placeholder, request)
// new async way so we can hide the spinner
jsreport.renderAsync(request).then((res) => {
res... // what goes here so we can render to placeholder div?
Loading.hide()
})