高德 web API 的 callba 应该怎么用？

API 接口 https://lbs.amap.com/api/webservice/guide/api/georegeo

返回数据

{"status":"1","info":"OK","infocode":"10000","count":"1","geocodes":[{"formatted_address":"北京市朝阳区阜通东大街 6 号","country":"中国","province":"北京市","citycode":"010","city":"北京市","district":"朝阳区","township":[],"neighborhood":{"name":[],"type":[]},"building":{"name":[],"type":[]},"adcode":"110105","street":"阜通东大街","number":"6 号","location":"116.482086,39.990496","level":"门牌号"}]}

比如我的 callback=getGPS

$.get('url', getGPS) ？？？

刚学到回调函数这，回调函数就是写好一个函数，当作参数传给另一个函数调用，那这个 callback 在这个 api 中有什么意义？应该怎么使用？

我现在直接

                   var results = $.get(url, getGeocodes);

                    function getGeocodes() {
                        var tude = results.responseJSON.geocodes[0].location;
                        $("#id_detect_coordinate").val(tude);
                    }
                }

我没有填那个 callback,直接拿到返回数据，所以那个 callback 到底有什么用？正确使用方法是什么？

maloneleo88

2022-05-08 23:18:56 +08:00

明白了。

```
//回调函数 getGPS
<script>
function getGPS(data) {
//do someting
}
</script>

<script src="请求地址巴拉巴拉&callback=回调函数">
</script>
```
没加 callback 服务器返回的是
```
{"status":"1","info":"OK","infocode":"10000","count":"1","geocodes":[{"formatted_address":"北京市朝阳区阜通东大街 6 号","country":"中国","province":"北京市","citycode":"010","city":"北京市","district":"朝阳区","township":[],"neighborhood":{"name":[],"type":[]},"building":{"name":[],"type":[]},"adcode":"110105","street":"阜通东大街","number":"6 号","location":"116.482086,39.990496","level":"门牌号"}]}
```
加了 callback 以后，服务器返回的是
```
getGPS({"status":"1","info":"OK","infocode":"10000","count":"1","geocodes":[{"formatted_address":"北京市朝阳区阜通东大街 6 号","country":"中国","province":"北京市","citycode":"010","city":"北京市","district":"朝阳区","township":[],"neighborhood":{"name":[],"type":[]},"building":{"name":[],"type":[]},"adcode":"110105","street":"阜通东大街","number":"6 号","location":"116.482086,39.990496","level":"门牌号"}]})
```

也就是说，服务器直接把回调函数名+(返回数据) 给返回来了。所以导致 getGPS(data)接收到的实参对象，所以执行 getGPS(data)，此时 data 从形参变实参了，在再回调函数中 do something

问题是，用$.get 直接拿数据不香吗？ API 这个回调函数的方式除了解决跨域还有啥用处？