Simple iterator using promises

iterator.js

(function (a) {
	
  'use strict'
  
  class Iterator {
    constructor() {
      this.tasks = []
      this.result = {}
    } 
    
    addTask(name, fn) {
      this.tasks.push(new Promise((resolve, reject) => {
        if (typeof name === 'function') {
          fn = name
          name = fn.name
        }
        
        if (fn.length === 0) {
          resolve({ name: name, value: fn() })
        }
        
        else {
          fn((err, res) => {
            if (err) return reject(err)
            resolve({ name: name, value: res })
          })
        }
        
      }))
    }
    
    setRes(res, next) {
      this.result[res.name] = res.value
      next()
    }
    
    run () {
      return new Promise((resolve, reject) => {
        let it = this.tasks[Symbol.iterator]()
        let next = () => {
          let item = it.next()
          if (item.done) return resolve(this.result)
          item.value
          	.then(res => this.setRes(res, next))
          	.catch(err => reject(err))
        }
        next()
      })
    }
  }
  
  a.Iterator = Iterator
  
})(window)