x.js

var addMember = map(memberEvents, function (event) {
    return function (state) {
        var members = extend(state.members)
        var value = event.value
        var widget = Member(value, input)

        membersHash[value.id] = value

        members[value.id] = {
            value: value
            , elem: widget.view
        }

        return {
            members: members
            , currentWidget: widget
        }
    }
})

var updateMember = map(modifyEvents, function (event) {
    return function (state) {
        var value = event.value
        var members = extend(state.members)
        var orig = members[value.id]

        members[value.id] = {
            value: extend(orig.value, value)
            , elem: orig.elem
        }

        return {
            members: members
            , currentWidget: null
        }
    }
})