How to use different cdn according to user's location?

Hello, guys. I'm using nuxt with nginx, I'm wondering how to make nuxt use different cdnUrl when nginx figure out whether a user is oversea. for example, I have uploaded all the static part of nuxt to both cdnUrls. I want nuxt use cdnUrl https://overseas.assets.com when user is from overseas and use https://common.assets.com when is not. Thanks