throttle through an AngularJS service. based on https://gist.github.com/mrgamer/6139485

angular-throttle.coffee

angular.module("app").factory "throttle", [
  "$timeout"
  ($timeout) ->
    return (delay, no_trailing, callback, debounce_mode) ->
      timeout_id = undefined
      last_exec = 0

      if typeof no_trailing isnt "boolean"
        debounce_mode = callback
        callback = no_trailing
        no_trailing = undefined

      wrapper = ->
        that = this
        elapsed = +new Date() - last_exec
        args = arguments
        exec = ->
          last_exec = +new Date()
          callback.apply that, args
          return

        clear = ->
          timeout_id = undefined
          return

        exec() if debounce_mode and not timeout_id
        $timeout.cancel timeout_id  if timeout_id

        if debounce_mode is undefined and elapsed > delay
          exec()
        else timeout_id = $timeout((if debounce_mode then clear else exec), (if debounce_mode is undefined then delay - elapsed else delay))  if no_trailing isnt true

        return

      wrapper
]