如何检查Google Maps API是否已加载？
问题描述：
如何检查Google Maps API（v3）是否已加载？
How to check if Google Maps API (v3) is loaded?
如果由于互联网连接问题导致API未加载，我不想执行映射脚本（网页托管在本地）。
I do not want to execute mapping scripts if the API did not load due to internet connectivity problems (web page is hosted locally).
答
if（google.maps）{...} 会给你一个参考错误，如果谷歌是未定义的（即如果API没有加载）。
if (google.maps) {...} will give you a reference error if google is undefined (i.e. if the API didn't load).
相反，使用 if（typeof google ==='object'&& typeof google.maps ==='object'）{...} 来检查它是否成功加载。
Instead, use if (typeof google === 'object' && typeof google.maps === 'object') {...} to check if it loaded successfully.