[рони]

Андрей М,

var cars = [
 {"year": "2012",
 "auto": "BMW"},
 {"year": "2015",
 "auto": "Volvo"},
 {"year": "2012",
 "auto": "Saab"},
 {"year": "2015",
 "auto": "Ford"}
 ];
var year = "2015";
var out = cars.filter(function(car) {
   return car.year == year
}).map(function(car) {
   return  car.auto
});
alert(JSON.stringify(out));