Javascript 使用typeahead.js的Google api自动完成预测不起作用

我想显示来自谷歌自动完成预测的提前输入建议

 var service = new google.maps.places.AutocompleteService();


          $('.delivery_areas').typeahead({
                highlight: true,
                minLength: 3,  

            },{

                name: 'predictions',
                limit: 6,
                async: true,
                source: function(q, sync,async) {
                    matches = [];
                    service.getPlacePredictions({
                        input: q
                    }, function(predictions, status) {
                        if (status == google.maps.places.PlacesServiceStatus.OK) {
                            predictions.forEach(function(prediction) {
                                matches.push(prediction.description);
                            });
                        }
                    });
                  //console.log(matches) display a list of suggestions from google
                  async(matches);
                 //cb(matches) also wont work  
                }
            });

不知何故，它对来自自动完成API的结果不起作用。 我尝试了同步和异步回调

---

注意：Typeahead在示例数据源中工作正常，API端也没有问题。结果即将到来，并存储在matches数组中。

回调不在正确的位置

$('.delivery_areas').typeahead({
                highlight: true,
                minLength: 3,  

            },{

                name: 'predictions',
                limit: 6,
                async: true,
                source: function(q, sync,async) {
                    matches = [];
                    service.getPlacePredictions({
                        input: q
                    }, function(predictions, status) {
                        if (status == google.maps.places.PlacesServiceStatus.OK) {
                            predictions.forEach(function(prediction) {
                                matches.push(prediction.description);
                            });
                         async(matches);
                        }
                    });

                }
            });