Function downloadPage

Picviewer CE+/Picviewer CE+.user.js:25557–25596

(url, post, headers, cb)

            }

            async function downloadPage(url, post, headers, cb) {
                var opts = {
                    method: 'GET',
                    url: url,
                    onload: function(req) {
                        try {
                            if(req.status > 399) throw 'Server error: ' + req.status;
                            else cb(req.responseText, req.finalUrl || url);
                        } catch(ex) {
                            if (!useFetch && req.responseHeaders.indexOf("cloudflare") != -1) {
                                useFetch = true;
                                return downloadPage(url, post, headers, cb);
                            }
                            handleError(ex);
                        }
                    },
                    onerror: handleError
                };
                if (post) {
                    opts.method = 'POST';
                    opts.data = post;
                    opts.headers = {'Content-Type':'application/x-www-form-urlencoded','Referer':url};
                }
                if (headers) {
                    if (typeof headers == 'function') {
                        headers = await headers(url + (post ? `#p{${post}}` : ""), xhr, getCookie);
                    }
                    opts.headers = headers;
                }

                if (useFetch) {
                    let fetchOption = {method: opts.method || 'GET', headers: opts.headers};
                    if (opts.method && opts.method != 'GET') {
                        fetchOption.body = opts.data || '';
                    }
                    fetch(opts.url, fetchOption).then(response => response.text()).then(data => {opts.onload({responseText: data})}).catch(e => opts.onerror(e));
                } else {
                    _GM_xmlhttpRequest(opts);
                }
            }

            function createDoc(text) {
                var doc = document.implementation.createHTMLDocument('PicViewerCE');