Weird google map error! can't pass new google.maps

Ionic Framework ionic-v3
1 
declare var google;


alert("creating map");
        location=new google.maps.LatLng(37.5665,126.9780)
        alert("!")

it’s weird.
It works very well on chrome but not on real device. android.
it alert creating map well but can’t see alert !
I installed plug in like below.

ionic cordova plugin add cordova-plugin-geolocation --variable GEOLOCATION_USAGE_DESCRIPTION=“To locate you”

npm install --save @ionic-native/geolocation