Bookmarklet to download all images of a given class

downloadbookmarklet.js

javascript: (function () {
    document.querySelectorAll('.BRpageimage').forEach(i => {
        const url = new URL(i.src);
        const filename = url.searchParams.get('file').split('/').pop().replace('.jp2','.jpg');
        url.searchParams.set('scale', 1);
        dl(url.href, filename);
    });

    function dl(url, filename) {
        function blob2B64(blob, callback) {
            const reader = new FileReader();
            reader.onloadend = function () {
                callback(reader.result);
            };
            reader.readAsDataURL(blob);
        }
        const req = new XMLHttpRequest();
        req.open('GET', `https://api.allorigins.win/raw?url=${encodeURIComponent(url)}`);
        req.responseType = 'blob';
        req.onload = event => {
            const blob = req.response;
            blob2B64(blob, b64 => {
                const a = document.createElement('a');
                document.body.appendChild(a);
                a.download = filename;
                a.href = b64;
                a.click();
            });
        };
        req.send();
    }
})();