Comment by npodbielski

   const result = data
     |> Object.entries(%)
     |> (%.filter(([k, v]) => v != null))
     |> Object.fromEntries(%)
     |> Object.values(%)
     |> JSON.stringify(%)
     |> encodeURIComponent(%);

Looks kinda awful to me. Am I strange that I prefer the 'spaghetti' version?