var objects = [
    [
        {"a":"foo","b":"baz"},
        {"a":"qux","b":"lam"}
    ],
    [
        {"a":"aafoo","b":"bbbbaz"},
        {"a":"aa2qux","b":"bbb2lam"}
    ]
];

var flattened = [].concat.apply(
    [],
    obs.map(
        objects => {
            return objects.map(
                o => {
                    return {a: o.b, b: o.a} })
        }))