With GMaps.js you can add elevation this way:
map.getElevations({
locations : [[-12.040397656836609,-77.03373871559225], [-12.050047116528843,-77.02448169303511], [-12.044804866577001,-77.02154422636042]],
callback : function (result, status){
if (status == google.maps.ElevationStatus.OK) {
console.log(result, status);
}
}
});