You can’t get google.maps.Map object from DOM Element ,on which Google Maps object have been constructed. google.maps.Map is just a wrapper, which controls DOM Element for viewing the map, and that element does not have reference to its wrapper.
If your problem is only the scope, make map as a property of window object, and it will be accessible from everywhere in your page. You can make 'map' as global by using one of these:
window.map = new google.maps.Map(..)
or
map = new google.maps.Map(...) //AVOID 'var'