function getFields(list, field, otherwise) {

    //  map the provided list to an array containing either the requested field or the alternative value

    return list.map(function(item) {

        //  If item is an object and contains the field, add its value and the value of otherwise if not

        return typeof item === 'object' && field in item ? item[field] : otherwise;

    }, []);

}

​

var myArray = [{foo: 1, bar: 2}, {bar: 3, baz: 4}, {foo: 5, baz: 6}];

​

//. no 'otherwise' (meaning it'll be undefined)

console.log(getFields(myArray, 'foo'));

​

//. otherwise=3

console.log(getFields(myArray, 'foo', 3));

​