async load google map api demo

index.jade

doctype html
html(lang="en")
  head
    title Map App

  body(ng-app="mapApp" animation="slide-left-right-ios7")
    ion-nav-bar.bar-light.shadow
    ion-nav-view(id="main")

    //- use init-map directive here
    init-map
    
    //- map directive here
    map

map.coffee

angular.module 'app.map', []

###
 Init map directive
 Use this in your  template
###
.directive 'initMap', ($window, $rootScope, $timeout) ->
    return {
        restrict: 'E'
        link: (scope, element, attr) ->
            # map callback function
            $window.mapInitialize = ->
                $rootScope.$broadcast 'mapInitialzied'

            # load script on window loaded
            $window.loadScript = ->
                script = document.createElement "script"
                script.type = "text/javascript"
                script.src = "https://maps.googleapis.com/maps/api/js?key=YOURKEYHERE&sensor=true&" +
                   "callback=mapInitialize"
                document.body.appendChild script

            $window.onload = loadScript
    }
    
###
 Map directive
###
.directive 'map', (Map, $rootScope, $window) ->
    return {
        restrict: 'E'
        scope:
            onCreate: '&'
        link: (scope, element, attr) ->

            ###
            load map when map is initialized
            ###
            loadMap = ->
                mapOptions =
                    zoom: 15
                    mapTypeId: $window.google.maps.MapTypeId.ROADMAP
                    disableDefaultUI: true
                    
                # create map instance
                map = new $window.google.maps.Map element[0], mapOptions

                scope.onCreate { map: map }

            initialize = ->
                # listen on map initialized event
                if not $window.google or not $window.google.maps
                    $rootScope.$on 'mapInitialzied', ->
                        loadMap()
                else
                    loadMap()

            initialize()
    }