how to convert this nested object into a flat object?

var test = {
    a: 'jack',
    b: {
        c: 'sparrow',
        d: {
            e: 'hahaha'
        }
    }
};

function traverseAndFlatten(currentNode, target, flattenedKey) {
    for (var key in currentNode) {
        if (currentNode.hasOwnProperty(key)) {
            var newKey;
            if (flattenedKey === undefined) {
                newKey = key;
            } else {
                newKey = flattenedKey + '.' + key;
            }

            var value = currentNode[key];
            if (typeof value === "object") {
                traverseAndFlatten(value, target, newKey);
            } else {
                target[newKey] = value;
            }
        }
    }
}

function flatten(obj) {
    var flattenedObject = {};
    traverseAndFlatten(obj, flattenedObject);
    return flattenedObject;
}

var flattened = JSON.stringify(flatten(test));
console.log(flattened);