Помогите скачать книги с сайта РГО!

function sleep2(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}
async function dump_book(cnt) {
    if (cnt <= 0) cnt = viewer.getPageManager().getPagesCount();
    if (cnt > viewer.getPageManager().getPagesCount() ) cnt = viewer.getPageManager().getPagesCount();
    var i;
    for (i = 1; i <= cnt; i++) {
        viewer.showPage(i);
        while (document.getElementsByClassName("page p"+ i + " loaded").length == 0) {
            await sleep2(2000);
        }
        var url = document.getElementsByClassName("page p"+ i + " loaded")[0].getElementsByTagName("img")[0].getAttribute("src");
        var filename = i+".jpg";
        while (filename.length < 10) filename = "0" + filename;
        var element = document.createElement('a');
        element.setAttribute('href', url);
        element.setAttribute('download', filename);
        element.style.display = 'none';
        document.body.appendChild(element);
        element.click();
    }
}

dump_book(5)

dump_book(0)

dump_book(очень большое число)

function sleepFor(sleepDuration){
    var now = new Date().getTime();
    while(new Date().getTime() < now + sleepDuration){ /* Do nothing */ }
}
var saveByteArray = (function () {
    var a = document.createElement("a");
    document.body.appendChild(a);
    a.style = "display: none";
    return function (data, name) {
        var blob = new Blob([data], {type: "octet/stream"}),
            url = window.URL.createObjectURL(blob);
        a.href = url;
        a.download = name;
        a.click();
        window.URL.revokeObjectURL(url);
        sleepFor(200);
    };
}());
function _base64ToArrayBuffer(base64) {
    var binary_string = window.atob(base64);
    var len = binary_string.length;
    var bytes = new Uint8Array(len);
    for (var i = 0; i < len; i++) {
        bytes[i] = binary_string.charCodeAt(i);
    }
    return bytes.buffer;
}
function _save_page(data)
{
var j = 1;
var page_no = data.key.substr(data.key.indexOf(":")+1, (data.key.lastIndexOf(":") - data.key.indexOf(":") - 1));
console.log(page_no);
for (j = 1; j <= data.slices.length-1; j++)
{
   var s = page_no + "_part_" + j + ".png";
   while (s.length < 16) s = "0" + s;
   var base64 = data.slices[j]; // skip j == 0
   base64 = base64.replace("data:image/png;base64,", "")
   base64 = base64.replaceAll("%0D", "")
   base64 = base64.replaceAll("%0A", "")
   console.log("save to " + s);
   console.log("size " + base64.length);
   saveByteArray(_base64ToArrayBuffer(base64), s);
}
}
var cnt = readercontrols.reader.pageCount();
var i = 1;
for(i =1; i <= cnt; i++)
{
reader2cache.storage("reader2viewer","page").getVal(readercontrols.reader.documentID() + ":" + i +":0",(_save_page));
}