Solo me preguntaba si esto es posible, creo que es buscando en Internet e hice mi intento a partir de estas fuentes.

 airport_data = [{"departure_time" :"12:00","arrival_time":"03:00","city_id":"BOS"}, {"departure_time" :"01:00","arrival_time":"04:00","city_id":"SFO"}, {"departure_time" :"03:00","arrival_time":"05:00","city_id":"BOS"}, {"departure_time" :"03:00","arrival_time":"05:00","city_id":"SFO"}, {"departure_time" :"04:00","arrival_time":"06:00","city_id":"SJC"}, {"departure_time" :"04:00","arrival_time":"06:00","city_id":"JFK"}, {"departure_time" :"06:00","arrival_time":"09:00","city_id":"SJC"}]; for(var i = 0; i < airport_data.length; i++) { if (airport_data.city_idindexOf(city.id[i])){ var counter_{airport_data.city_id} += 1; } }

Meta

 counter_BOS = 2; counter_SFO = 1; counter_SJC = 2; counter_JFK = 1; counter_JFC = 1;