This approach works with mostly static or server-side generated websites, but with JS-heavy SPA unsupported browsers would be just showing a blank page. Curren

This approach works with mostly static or server-side generated websites, but with JS-heavy SPA unsupported browsers would be just showing a blank page. Currently I'm checking whether the browser supports Custom Elements v1, Shadow DOM v1 and HTML imports. If it does not, I'm showing the fallback page.