Stream.Readable で インターバルタイマー

Timer.js

'use strict'
var stream = require('stream')
var util   = require('util')
var types  = {
    '"timeout" must be "Number"':  function (n) { return isNaN(n) }
  , '"timeout" must be "Int".':    function (n) { return (n + '').indexOf('.') !== -1 }
  , '"timeout" must be over "0".': function (n) { return n < 0 }
}

function Timer (timeout, _opt) {
    timeout = Number(timeout)

    for (var p in types) {
        if (types[p](timeout)) throw new TypeError(p)
    }

    stream.Readable.call(this, _opt)
    this.timeout  = timeout
    this.index    = 0
    this.interval = 500
}

util.inherits(Timer, stream.Readable)

Timer.prototype._read = function () {
    setTimeout(function () {
        var i = (this.index += 1)
        i > this.timeout ? this.push(null) : this.push(new Buffer(i + ''))
    }.bind(this), this.interval)
}

module.exports = Timer