xstream version

xstream.js

function todoList (deferred) {
    const ping$ = xs.create({
        start: function (listener) {
            setTimeout(() => {
                ;[...Array(config.iterations).keys()].forEach(i =>
                    listener.next(i)
                )
            }, 0)
        },

        stop: function () {}
    })
    const todo$ = ping$.map(todo)
    const old$ = todo$.filter(todo => todo.id % 4 === 0).startWith({})
    const sample$ = sampleCombine(old$)(todo$).map(([last, old]) => ({
        ...last,
        old
    }))
    const list$ = sample$.fold((list, item) => [...list, item], [])
    const end$ = list$.filter(list => list.length === config.iterations).take(1)
    return end$.map(res => deferred.resolve(res))
}