zundoko.js

var Rx = require('rx')

var source0 =
    Rx.Observable.timer(0, 500)
    .map(function () {
        if(Math.floor(Math.random() * 2) == 0){
            return 'ズン'
        }else{
            return 'ドコ'
        }
    })
    .share()
var source1 = Rx.Observable.return('').concat(source0)
var source2 = Rx.Observable.return('').concat(source1)
var source3 = Rx.Observable.return('').concat(source2)
var source4 = Rx.Observable.return('').concat(source3)

var source =Rx.Observable.zip(source4, source3, source2, source1, source0)

var logger = Rx.Observer.create(
    function (data) {
        process.stdout.write(data)
    })

source4.subscribe(logger)

source.subscribe(Rx.Observer.create(
    function(data) {
        var expected = ['ズン', 'ズン', 'ズン', 'ズン', 'ドコ']
        for(var i = 0;i < expected.length;i ++) {
            if(expected[i] !== data[i]) {
                return
            }
        }
        logger.onNext('キヨシ')
        logger.onCompleted()
        process.exit()
    }))