const Readable = require('stream').Readable; class Subscription extends Readable{ constructor(options) { super(); if (!(this instanceof Subscription)) return new Subscription(options); options = options || {}; Readable.call(this, options); this.value = 0; } _read() { while(this.value <= 100){ this.push(String(this.value++)); } } } exports.subscribe = function(event, options){ return new Subscription(options); }