Angular Worker-based Interval (to avoid Chrome background tab throttling)

interval-worker.js

var timers = {}

function fireInterval(id) {
  this.postMessage({id: id})
}

var commands = {
  setInterval: function W_setInterval(data) {
    var time = parseInt(data.time || 0, 10)
    timer = setInterval(fireInterval.bind(null, data.id), time)
    timers[data.id] = timer
  },
  clearInterval: function W_clearInterval(data) {
    if (timers[data.id]) {
      clearInterval(timers[data.id])
      delete timers[data.id]
    }
  }
}

this.addEventListener('message', function(event) {
  var data = event.data
  if (commands[data.command]) {
    commands[data.command](data)
  }
})

winterval.js

// $interval + Web Worker
// to avoid background timer throttling by Chrome (and maybe other browsers)
// heavily adapted from https://gist.github.com/BinaryMuse/19aa812cd2277d8c9555
// returns an object that mostly behaves like $interval
//    EXCEPT it just returns an id, not a promise
//    (there may be other differences, but most of them would be downstream of this one)
//
// in browsers that don't support Worker, it just returns the $interval module
// either way, whatever it returns is still the thing to pass to .cancel()
app.provider('winterval', function WintervalProvider() {
  function isDefined(value) {return typeof value !== 'undefined'}

  this.$get = ['$rootScope', '$interval',
       function($rootScope,   $interval) {
    if (typeof(Worker) == 'undefined') {
      return $interval
    }
    var timers = {}
    var intervalId = 0
    
    var worker = new Worker('/interval-worker.js')
    worker.addEventListener('message', function (event) {
      var data = event.data
      var id = data.id
      var timer = timers[id]
      if (timer) {
        var count = timer.count
        var fn = timer.fn
        var args = timer.args

        if (timer.count > 0 && timer.iteration >= timer.count) {
          worker.postMessage({command: "clearInterval", id: id})
          delete timers[id]
        }

        if (!timer.skipApply) $rootScope.$apply()

        fn.apply(null, args)
      } else {
        console.log("worker attempted to access nonexistent timer")
        worker.postMessage({command: "clearInterval", id: id})
      }
    })

    function winterval(fn, delay, count, invokeApply) {
      intervalId += 1
      delay = delay || 0
      var id = intervalId
      timers[id] = {
        fn: fn,
        iteration: 0,
        count: isDefined(count) ? count : 0,
        skipApply: (isDefined(invokeApply) && !invokeApply)
        // args: args
      }
      worker.postMessage({command: "setInterval", id: id, time: delay, count: count})
      return id
    }

    winterval.cancel = function (id) {
      if (timers[id]) {
        worker.postMessage({command: "clearInterval", id: id})
        delete timers[id]
        return true
      }
      return false
    }

    return winterval
 }]
})