Promise Task Scheduler

promise-task-scheduler.js

var Promise = require('bluebird')
var lodash = require('lodash')

var _queue = {}

function addTask(key, promiseFactory, leading, wait) {
  if (!key) {
    throw new Error('Missing key: ' + key)
  }

  var resolve
  var reject
  var promise = new Promise(function(deferredResolve, deferredReject) {
    resolve = deferredResolve
    reject = deferredReject
  })

  var task = _queue[key]

  if (!task) {
    var callback = function(promiseFactory, resolve, reject) {
      promiseFactory().then(resolve, reject)
    }

    var options = {
      leading: leading,
      trailing: true
    }

    task = lodash.debounce(callback, wait || 500, options)

    _queue[key] = task
  }

  task(promiseFactory, resolve, reject)

  return promise
}

addTask('a', function() {
  return Promise.resolve('foo')
}).then(function(result) {
  console.log(result)
})

addTask('a', function() {
  return Promise.resolve('bar')
}).then(function(result) {
  console.log(result)
})