How to sort array in javascript based on number of sub childs of objects : What is the best way to sort the following array in order on number of sub childs (i.e. isbns in this case).

    data:[
    {
        {
            " Arnold Bennett": {
                "9781784872359": {
                    "thumbnail_image_url": "https://books-sn.s3.amazonaws.com/571b8c01-ed88-4cc1-8e0c-efe3de967147.jpg",
                    "title": "Clayhanger "
                }
            }
        },
        "Agatha Christie": {
            "9780007527588": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=BxlamwEACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api",
                "title": "Mrs. McGinty's Dead"
            },
            "9780008129590": {
                "thumbnail_image_url": "https://books-sn.s3.amazonaws.com/c125ee1d-c5ea-4827-a488-e9ee9c8afc8d.jpg",
                "title": "The Clocks"
            },
            "9780007120857": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=RAlvswEACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api",
                "title": "The Murder at the Vicarage"
            },
            "9780007556878": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=Zb_inQEACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api",
                "title": "Dead Man's Folly"
            },
            "9780007120826": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=Dve45zlLKbUC&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api",
                "title": "4.50 from Paddington"
            },
            "9780007121052": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=QR9J95ZE2zcC&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api",
                "title": "Nemesis"
            },
            "9780007527519": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=dOrsAQAACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api",
                "title": "Five Little Pigs"
            },
            "9780007120963": {
                "thumbnail_image_url": "https://books-sn.s3.amazonaws.com/ba1fcb40-5383-40d9-bdfc-0e9d285b2321.jpeg",
                "title": "A Murder is Announced "
            },
            "9780008196233": {
                "thumbnail_image_url": "https://books-sn.s3.amazonaws.com/3a08b20a-377e-4b96-890c-1ecc3e09e595.jpg",
                "title": "The Sittaford Mystery"
            },
            "9780008196615": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=6E8FvgAACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api",
                "title": "At Bertram's Hotel"
            },
            "9780008129484": {
                "thumbnail_image_url": "https://books-sn.s3.amazonaws.com/fe46e96d-7f24-40f1-92e1-b60f10af9dd1.jpg",
                "title": "The Mystery of the Blue Train"
            },
            "9780007314669": {
                "thumbnail_image_url": "https://books-sn.s3.amazonaws.com/cd40bc91-4c28-4f97-872a-ba24f10b0564.jpg",
                "title": "An Autobiography"
            },
            "9780006513773": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=JMqChKyf-0EC&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api",
                "title": "Hercule Poirot"
            },
            "9780007527502": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=9CO1mgEACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api",
                "title": "Murder on the Orient Express"
            },
            "9780007527496": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=ERPosgEACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api",
                "title": "The Mysterious Affair at Styles"
            },
            "9780007120833": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=lA1KuAEACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api",
                "title": "The Body in the Library"
            },
            "9780007120734": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=CEEUPYluIeEC&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api",
                "title": "Five Little Pigs"
            },
            "9780007120970": {
                "thumbnail_image_url": "https://books-sn.s3.amazonaws.com/fd1f1d09-c08f-4f35-8be1-a35862d9e4b6.jpg",
                "title": "A Pocket Full of Rye"
            },
            "9780007120864": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=MK9JNwoZAncC&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api",
                "title": "The Thirteen Problems"
            },
            "9780008125929": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=kxK7rQEACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api",
                "title": "The Secret Adversary (隱身魔鬼)"
            },
            "9780007121069": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=ddlQBfuKWzwC&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api",
                "title": "Sleeping Murder"
            },
            "9780008164898": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=JCX2sgEACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api",
                "title": "Cards on the Table"
            }
        }
    },
    {
        "Alain De Botton": {
            "9780141035192": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=l4FGPwAACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api",
                "title": "The Consolations of Philosophy"
            }
        }
    },
    {
        "Alan Hollinghurst": {
            "9781447275183": {
                "thumbnail_image_url": "https://books-sn.s3.amazonaws.com/b46fc3f6-4950-4e4d-a734-93abd10b5351.jpeg",
                "title": "The Line of Beauty"
            }
        }
    },
    {
        "Alan MacDonald": {
            "9781407108315": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=1aEGOwAACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api",
                "title": "Winston Churchill and His Woeful Wars"
            }
        }
    },
    {
        "Aldous Huxley": {
            "9780099518471": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=3zl4oJMUskoC&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api",
                "title": "Brave New World"
            }
        }
    },
    {
        "Alessandro Manzoni": {
            "9780140442748": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=azLiQUtMSncC&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api",
                "title": "The Betrothed"
            },
            "9780241259078": {
                "thumbnail_image_url": "http://books.google.com/books/content?id=nyo8jwEACAAJ&printsec=frontcover&img=1&zoom=1&source=gbs_api",
                "title": "The Betrothed"
            }
        }
    }
]

I want to sort so that I get Agatha Christie on top and then Alessandro Manzoni and then the rest of them in order of child elements they have.

Thanks