Simplify filter a lot

[oliverjam]

There's probably a simpler way to achieve the filtering: your client-side JS currently fetches an HTML response, then replaces the entire content of the page with that HTML response.

This is essentially what an anchor tag does by default: when the user clicks it the browser sends a GET request to the URL in the href property, and then shows the HTML response as a new page.

So if you give your filter links hrefs like <a href="/filter?f=work"> etc then you could access that querystring value in the handler for the /filter endpoint and send the right response. You wouldn't need any client-side JS at all