Question

我提前道歉，因为我觉得这是一个很简单的问题，但我是新的，所以我不太明白该怎么做！

我正在对地址进行地理编码，然后返回坐标：

//Geocoder
var geocoder = new google.maps.Geocoder();

//Submit listener and alert the coordinates
submit.addEventListener('click', function() {
    alert(geocodeAddress(geocoder, map)));
});

//Geocodes an address and returns the lat lng
function geocodeAddress(geocoder, resultsMap) {
    geocoder.geocode({address: address.value}, function(addressLatLng, status) {

        //Checks if status returned was ok
        if (status === google.maps.GeocoderStatus.OK) {

            //adds pin to map and centers map on pin
            resultsMap.setCenter(addressLatLng[0].geometry.location);
            var marker = new google.maps.Marker({
                map: resultsMap,
                position: addressLatLng[0].geometry.location
            });
            //alert(addressLatLng[0].geometry.location);
            return(addressLatLng[0].geometry.location);
        } else {
            alert('No address was found, please try again!');
        }
    });
}

如果我在函数内部提醒他们，它会正确地提醒他们（即{20.12345,20.12345}。如果我在提交按钮上提醒他们，它只是说＆＃34;未定义。＆＃34;我如何正确返回那些坐标？（我最终必须对它们做些什么，而不仅仅是警告它们）谢谢！

Answer 1

这应该有效

//Geocoder
var geocoder = new google.maps.Geocoder();

//Submit listener and alert the coordinates
submit.addEventListener('click', function() { //This is callback
    geocodeAddress(geocoder, map, function(loc){
      alert(loc || 'No address was found, please try again!');   
    });
});

//Geocodes an address and returns the lat lng
function geocodeAddress(geocoder, resultsMap, cb) {
    geocoder.geocode({address: address.value}, function(addressLatLng, status) {

        //Checks if status returned was ok
        if (status === google.maps.GeocoderStatus.OK) {

            //adds pin to map and centers map on pin
            resultsMap.setCenter(addressLatLng[0].geometry.location);
            var marker = new google.maps.Marker({
                map: resultsMap,
                position: addressLatLng[0].geometry.location
            });
             //call cb with location details
            cb(addressLatLng[0].geometry.location);
        } else {
            //call the callback with empty value
            cb('');
        }
    });
}

希望这有帮助！

Answer 2

我认为这是一个异步问题。您需要从函数返回Promise，然后在履行承诺时调用警报。

警报显示未定义的原因是因为该功能尚未完成，因此在显示警报时尚未返回。

返回javascript对象警告＆＃34; undefined＆＃34;

2 个答案: