javascript 获取“未捕获的类型错误：无法读取未定义”错误的属性“地理编码”
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Getting 'Uncaught TypeError: Cannot read property 'geocode' of undefined ' error
提问by Praveen Rawat
When i am running the following code, which i have taken from thisanswer, i am getting Uncaught TypeError: Cannot read property 'geocode' of undefinederror in browser's console, why its happening because on the body load here initializefunction has to be called, and instead of calling initializefunction here codeLatLng(lat, lng)is calling first.
当我运行以下代码（我从这个答案中获取）时，我Uncaught TypeError: Cannot read property 'geocode' of undefined在浏览器的控制台中收到错误，为什么会发生错误，因为必须在此处initialize调用主体加载函数，而不是首先调用initialize此处的函数codeLatLng(lat, lng)。
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="initial-scale=1.0, user-scalable=no"/>
<meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
<title>Reverse Geocoding</title>
<script type="text/javascript" src="http://maps.googleapis.com/maps/api/js?sensor=false"></script>
<script type="text/javascript">
var geocoder;
if (navigator.geolocation) {
navigator.geolocation.getCurrentPosition(successFunction, errorFunction);
}
//Get the latitude and the longitude;
function successFunction(position) {
var lat = position.coords.latitude;
var lng = position.coords.longitude;
codeLatLng(lat, lng)
}
function errorFunction(){
alert("Geocoder failed");
}
function initialize() {
geocoder = new google.maps.Geocoder();
}
function codeLatLng(lat, lng) {
var latlng = new google.maps.LatLng(lat, lng);
geocoder.geocode({'latLng': latlng}, function(results, status) {
if (status == google.maps.GeocoderStatus.OK) {
console.log(results)
if (results[1]) {
//formatted address
alert(results[0].formatted_address)
//find country name
for (var i=0; i<results[0].address_components.length; i++) {
for (var b=0;b<results[0].address_components[i].types.length;b++) {
//there are different types that might hold a city admin_area_lvl_1 usually does in come cases looking for sublocality type will be more appropriate
if (results[0].address_components[i].types[b] == "administrative_area_level_1") {
//this is the object you are looking for
city= results[0].address_components[i];
break;
}
}
}
//city data
alert(city.short_name + " " + city.long_name)
} else {
alert("No results found");
}
} else {
alert("Geocoder failed due to: " + status);
}
});
}
</script>
</head>
<body onload="initialize()">
</body>
</html>
回答by Dr.Molle
There is no need to wait for the onload-event until you initialize the Geocoder-instance. You load the maps-API synchronously, so the API(including google.maps.Geocoder) is available immediately after loading the API.
在初始化 Geocoder-instance 之前，无需等待 onload-event。您同步加载 maps-API，因此google.maps.Geocoder加载 API 后API（包括）立即可用。
The issue: when geolocation runs too fast, and the callback of navigator.geolocation.getCurrentPositionwill be executed before the onload-event, geocoder is undefined.
问题：当 geolocation 运行太快，并且 的回调navigator.geolocation.getCurrentPosition将在 onload-event 之前执行，geocoder 是undefined.
Replace this line:
替换这一行：
var geocoder;
with this line:
用这一行：
var geocoder = new google.maps.Geocoder();
