Pattern to create a Readable Stream

readable-pattern.js

// Example based in Substack Stream Handbook:
// https://github.com/substack/stream-handbook#creating-a-readable-stream

'use strict'

var inherits = require('inherits')
var duplexify = require('duplexify')
var Stream = require('readable-stream').Stream

var CONST = {
  START: 64,
  END: 75
}

// Option 1: based on composition
module.exports = function () {
  var stream = Stream.Readable()
  var counter = Number(CONST.START)

  stream._read = function () {
    var _this = this
    var iv = setInterval(function () {
      if (++counter < CONST.END) return _this.push(String.fromCharCode(counter))
      clearInterval(iv)
      _this.push(null)
    }, 50)
  }
  return stream
}

// Option 2: based on inheritance
function KeyOutputStream () {
  if (!(this instanceof KeyOutputStream)) return new KeyOutputStream()
  Stream.Readable.call(this)
  this.counter = Number(CONST.START)
}

module.exports = KeyOutputStream
inherits(KeyOutputStream, Stream.Readable)

KeyOutputStream.prototype._read = function () {
  var _this = this
  var iv = setInterval(function () {
    if (++_this.counter < CONST.END)
      return _this.push(String.fromCharCode(_this.counter))
    clearInterval(iv)
    _this.push(null)
  }, 50)
}