firebase iterate object
firebase.database().ref("profile/user_id").on('value', function(snap){
snap.forEach(function(childNodes){
//This loop iterates over children of user_id
//childNodes.key is key of the children of userid such as (20170710)
//childNodes.val().name;
//childNodes.val().time;
//childNodes.val().rest_time;
//childNodes.val().interval_time;
});
});