One of the most pleasant experiences I had writing code, is early AI days when we did hyperscript SSE. Super locality of behavior, super interesting way of writing Server Sent Events code.

eventsource demo from http://server/demo

    on message as string
        put it into #div
    end

    on open
        log "connection opened."
    end

    on close
        log "connection closed."
    end

    on error
        log "handle error here..."
    end

end https://hyperscript.org/features/event-source/