GM_fetch — a wrapper for GM_xmlhttpRequest of TamperMonkey and ViolentMonkey UserScript extensions.
GM_fetch is compatible with Fetch API.
Currently it is in development. So, it's not complited.
The more detail description will be later.
Okay, if you just need a simple wrapper, here is it:
async function GM_fetch(url, {method = "get", headers} = {}) {
return new Promise((resolve, _reject) => {
const blobPromise = new Promise((resolve, reject) => {
GM_xmlhttpRequest({
url,
method,
headers,
responseType: "blob",
onload: response => resolve(response.response),
onerror: reject,
ontimeout: reject,
onreadystatechange: onHeadersReceived
});
});
blobPromise.catch(_reject);
function onHeadersReceived(response) {
const {
readyState, responseHeaders, status, statusText
} = response;
if (readyState === 2) { // HEADERS_RECEIVED
const headers = parseHeaders(responseHeaders);
resolve({
headers,
status,
statusText,
ok: status.toString().startsWith("2"),
arrayBuffer: () => blobPromise.then(blob => blob.arrayBuffer()),
blob: () => blobPromise,
json: () => blobPromise.then(blob => blob.text()).then(text => JSON.parse(text)),
text: () => blobPromise.then(blob => blob.text()),
});
}
}
});
}
function parseHeaders(headersString) {
class Headers {
get(key) {
return this[key.toLowerCase()];
}
}
const headers = new Headers();
for (const line of headersString.trim().split("\n")) {
const [key, ...valueParts] = line.split(":"); // last-modified: Fri, 21 May 2021 14:46:56 GMT
headers[key.trim().toLowerCase()] = valueParts.join(":").trim();
}
return headers;
}It supports only method and headers keys of fetch's options parameter.
Demo for the simple wrapper (gm_fetch_simple_demo.user.js):
// ...
// @grant GM_xmlhttpRequest
// ==/UserScript==
(async function demo() {
const url = "https://i.imgur.com/2wD3VJA.jpg";
const refererHeader = "https://imgur.com/";
const response = await GM_fetch(url, {headers: {referer: refererHeader}});
const {status, statusText, ok} = response;
const lastModified = response.headers.get("last-modified");
console.log(url, {status, statusText, ok, lastModified});
const blob = await response.blob();
const name = url.split("/").pop();
downloadBlob(blob, name, url);
})();
function downloadBlob(blob, name, url) {
const anchor = document.createElement("a");
anchor.setAttribute("download", name || "");
const blobUrl = URL.createObjectURL(blob);
anchor.href = blobUrl + (url ? ("#" + url) : "");
anchor.click();
setTimeout(() => URL.revokeObjectURL(blobUrl), 5000);
}
// ...
// async function GM_fetch(url, init = {}) {
// ...- https://www.tampermonkey.net/documentation.php#GM_xmlhttpRequest
- https://violentmonkey.github.io/api/gm/#gm_xmlhttprequest
- https://wiki.greasespot.net/GM.xmlHttpRequest