Best way to get intersection of keys of two objects?

var firstObject = { x: 0, y: 1, z: 2, a: 10, b: 20, e: 30 },
    secondObject = { x: 0, y: 1, z: 2, a: 10, c: 20, d: 30 };

function intersection(o1, o2) {
    return Object.keys(o1).concat(Object.keys(o2)).sort().reduce(function (r, a, i, aa) {
        if (i && aa[i - 1] === a) {
            r.push(a);
        }
        return r;
    }, []);
}

document.write('<pre>' + JSON.stringify(intersection(firstObject, secondObject), 0, 4) + '</pre>');

var firstObject = { x: 0, y: 1, z: 2, a: 10, b: 20, e: 30 },
    secondObject = { x: 0, y: 1, z: 2, a: 10, c: 20, d: 30 };

function intersection(o1, o2) {
    return Object.keys(o1).filter({}.hasOwnProperty.bind(o2));
}

document.write('<pre>' + JSON.stringify(intersection(firstObject, secondObject), 0, 4) + '</pre>');