accumulate.js

var foldp = require("signal/foldp")
var merge = require("signal/merge")

// accumulate :: [Signal<Function(S -> S)>] -> S -> Signal<S>
module.exports = accumulate

// accumulate take a list of signals of functions that take previous
// state and returns some new state and also takes the initial
// state. It will return a signal of the current state as applied
// by those functions
function accumulate(args, initial) {
    return foldp(merge(args), function (state, fn) {
        return fn(state)
    }, initial)
}

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]

        if (!orig) {
            return { members: members }
        }

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

        return { members: members }
    }
})

var state = accumulate([ addMember, updateMember ], {
    members: {}
    , currentWidget: null
})