Using for..in
to iterate object and reduce
to iterate array
var data = [{costOfAirtickets: 2500, costOfHotel: 1200},{costOfAirtickets: 1500, costOfHotel: 1000}];
var result = [data.reduce((acc, n) => {
for (var prop in n) {
if (acc.hasOwnProperty(prop)) acc[prop] += n[prop];
else acc[prop] = n[prop];
}
return acc;
}, {})]
console.log(result)