试图在Magento中使用谷歌地图方向的错误(未捕获的ReferenceError:谷歌未定义)

我专门创建了一个使用Google导航的方向模板文件。我有剧本外Magento工作。不幸的是，当我把脚本移动到页面/方向。php控制台返回以下错误:

"Uncaught ReferenceError: google is not defined"

当我尝试单击触发calcRoute()函数的test时，我得到以下错误:

"未捕获的TypeError: Cannot call method 'route' of undefined"

我认为这些错误与谷歌地图API调用有关，但是图形地图在页面上显示和运行良好。这些错误与google.maps.DirectionsService()被调用来定义如下所示的javascript的第2行directionsService和directionsService有关。路由在最后被调用。两者都与方向有关。

为什么地图显示，但方向抛出错误时，脚本工作是在我的html测试?我很困惑。

Javascript

  var directionDisplay;
  var directionsService = new google.maps.DirectionsService();
  var map;
  function directionsMap() {
    directionsDisplay = new google.maps.DirectionsRenderer();
    var chicago = new google.maps.LatLng(38.77627, -95.910965);
    var mapOptions = {
      zoom:4,
      mapTypeId: google.maps.MapTypeId.ROADMAP,
      center: chicago
    }
    map = new google.maps.Map(document.getElementById('map-directions'), mapOptions);
    directionsDisplay.setMap(map);
    //Place Markers
    var baldwinsvilleMarker = new google.maps.Marker({
        position: new google.maps.LatLng(00.00000, 00.00000),
        map: map,
        title:"store location 1"
    });
    var sacramentoMarker = new google.maps.Marker({
        position: new google.maps.LatLng(00.00000, 00.00000),
        map: map,
        title:"store location 2"
    });
    var stLouisMarker = new google.maps.Marker({
        position: new google.maps.LatLng(000.00000, -000.00000),
        map: map,
        title:"store location 3"
    });
    var catersvilleMarker = new google.maps.Marker({
        position: new google.maps.LatLng(00.000000, -84.000000),
        map: map,
        title:"store location 4"
    });
    directionsDisplay.setMap(map);
    directionsDisplay.setPanel(document.getElementById("get-directions"));
  }
  function calcRoute() {
    console.log("calcRoute ran")
    var start = document.getElementById('start').value;
    var end = document.getElementById('end').value;
    console.log(start + ' ' + end)
    var request = {
        origin:start,
        destination:end,
        travelMode: google.maps.DirectionsTravelMode.DRIVING
    };
    directionsService.route(request, function(response, status) {
      if (status == google.maps.DirectionsStatus.OK) {
        directionsDisplay.setDirections(response);
      }
    });
  }

           #I am including this line in the document head
           <script src="https://maps.googleapis.com/maps/api/js?v=3.exp&sensor=false"></script>
           <style onload="directionsMap()">
            #map-directions{width: 65%; height: 300px; float: left; border:5px solid #EEEEEE;}
            #get-directions{width: 65%; float: left;}
            .map-sidebar{width: 32%; height: 300px; float: right;}
            </style>
            <div id="map-directions"></div>
            <div class="map-sidebar">
                <h2>Get Directions</h2>
                <input type="text" id="start" value="chicago, il"/>
                <b>End: </b>
                <select id="end" onchange="calcRoute();">
                  <option value="value 1">
                      store location 1
                  </option>
                  <option value="value 2">
                      store location 2
                  </option>
                  <option value="value 3">
                      store location 3
                  </option>
                  <option value="value 4">
                      store location 4
                  </option>
                </select>
                <button onclick="calcRoute();"> test</button>

            </div>
            <div id="get-directions"></div>

$(function() {
   directionsMap()
});