为什么这个变量未定义或没有返回？ [英] Why is this variable undefined or not returned?

问题描述

我有以下代码：

I have the following code:

/*
 * converts a string to geolocation and returns it
 */

function stringToLatLng(string){
    if(typeof string == "string"){
        geocoder = new google.maps.Geocoder();
        geocoder.geocode( { 'address': string}, function(results, status) {
           if (status == google.maps.GeocoderStatus.OK) {
              console.log("LatLng: "+results[0].geometry.location);
              return results[0].geometry.location;
           } else {
              console.log("Geocode was not successful for the following reason: " + status);
           }
        });
   }
}

LatLng将正确的位置打印到控制台，但当我写这篇文章时：

the LatLng prints the correct location to the console, but when I write this:

var pos = stringToLatLng('New York');
            console.log(pos);

我得到 undefined 返回。这是为什么？谢谢

I get undefined back. Why is that? thanks

推荐答案

类似于这样的内容：

Something like this:

function stringToLatLng(strloc, callback){
    if(typeof string == "string"){
        geocoder = new google.maps.Geocoder();
        geocoder.geocode( { 'address': strloc}, function(results, status) {
           if (status == google.maps.GeocoderStatus.OK) {
              callback.call({}, results[0].geometry.location);
           } else {
              console.log("Geocode was not successful for the following reason: " + status);
           }
        });
   }
}

stringToLatLng('New York', function(pos){
    console.log(pos);
});

在您的代码中，当您返回时，您实际上是从函数（结果，状态）{ ..}函数，而不是stringToLatLng函数，正如在注释中说的那样，它是一个异步调用，所以你必须使用回调函数。

In your code, when you return, you are actually returning from the function(results, status){..} function, not the stringToLatLng function, as said in the comments its an asynchronous call, so you must use a callback.

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