x.js

        function (x) {
            return {
                status: x.online ? "online" : "offline"
            }
        }

function (x) { return x.online }

        function (curr, changed) {
            return { online: changed.online }
        }

        function (ev) {
            return { online: ev.target.checked }
        }

    function (x) {
        return x.value.type === "colingo-feed::course~members" &&
            x.eventType === "add"
    }