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GM_download Polyfill

A polyfill to make your userscript supports GM_download

Version vom 08.07.2016. Aktuellste Version

Dieses Skript sollte nicht direkt installiert werden. Es handelt sich hier um eine Bibliothek für andere Skripte, welche über folgenden Befehl in den Metadaten eines Skriptes eingebunden wird // @require https://update.greasyfork.org/scripts/21234/135567/GM_download%20Polyfill.js 

// ==UserScript==
// @name        GM_download Polyfill
// @namespace   GM_downloadpolyfill
// @author      MegaByte
// @description A polyfill to make your userscript supports GM_download
// @run-at      document-start
// @version     2.2.2
// @grant 		GM_xmlhttpRequest
// ==/UserScript==


/*
 *  GM_download polyfill
 *  
 *  @description  A polyfill to make your userscript supports GM_download
 *  @author       ccloli
 *  @version      1.0
 */

// to use this polyfill, you must add "@grant GM_xmlhttpRequest" at userscript metadata block

// Original Documentation: http://tampermonkey.net/documentation.php?ext=dhdg#GM_download

if (typeof GM_download !== 'function') {
    if (typeof GM_xmlhttpRequest !== 'function') {
        throw new Error('GM_xmlhttpRequest is undefined. Please set @grant GM_xmlhttpRequest at metadata block.');
    }

    function GM_download (url, name) {
        if (url == null) return;

        var data = {
            method: 'GET',
            responseType: 'arraybuffer',

            onload: function (res) {
                var blob = new Blob([res.response], {type: 'application/octet-stream'});
                var url = URL.createObjectURL(blob); // blob url

                var a = document.createElement('a');
                a.setAttribute('href', url);
                a.setAttribute('download', data.name != null ? data.name : 'filename');
                document.documentElement.appendChild(a);
                
                // call download
                // a.click() or CLICK the download link can't modify filename in Firefox (why?)
                // Solution from FileSaver.js, https://github.com/eligrey/FileSaver.js/
                var e = new MouseEvent('click');
                a.dispatchEvent(e);

                document.documentElement.removeChild(a);

                setTimeout(function(){
                    // reduce memory usage
                    URL.revokeObjectURL(url);
                    if ('close' in blob) blob.close(); // File Blob.close() API, not supported by all the browser right now
                    blob = undefined;
                }, 1000);

                if (typeof data.onafterload === 'function') data.onafterload(); // call onload function
            }

            // error object of onerror function is not supported right now
        };

        if (typeof url === 'string') {
            data.url = url;
            data.name = name;
        }
        else {
            if (url instanceof Object === false) return;

            // as documentation, you can only use [url, name, headers, saveAs, onload, onerror] function, but we won't check them
            // Notice: saveAs is not supported
            if (url.url == null) return;

            for (var i in url) {
                if (i === 'onload') data.onafterload = url.onload; // onload function support
                else data[i] = url[i];
            }
        }

        // it returns this GM_xhr, thought not mentioned in documentation
        return GM_xmlhttpRequest(data);
    }
}