refactor: get sandbox window using GM APIs

src/gm.ts

@@ -8,6 +8,9 @@ declare const GM: {
 
   /** https://www.tampermonkey.net/documentation.php#GM_registerMenuCommand */
   registerMenuCommand (name: string, fn: () => any, accessKey?: string): Promise<number>;
+
+  /** https://github.com/Tampermonkey/tampermonkey/issues/881#issuecomment-639705679 */
+  addElement<K extends keyof HTMLElementTagNameMap> (tagName: K, properties: Record<string, any>): Promise<HTMLElementTagNameMap[K]>;
 }
 export const _GM = GM
 

src/meta.js

@@ -14,5 +14,6 @@
 // @copyright    Copyright (c) 2019-2020 Xmader
 // @grant        unsafeWindow
 // @grant        GM.registerMenuCommand
+// @grant        GM.addElement
 // @run-at       document-start
 // ==/UserScript==

src/utils.ts

@@ -1,5 +1,6 @@
 
 import isNodeJs from 'detect-node'
+import { isGmAvailable, _GM } from './gm'
 
 export const escapeFilename = (s: string): string => {
   return s.replace(/[\s<>:{}"/\\|?*~.\0\cA-\cZ]+/g, '_')
@@ -60,6 +61,13 @@ export const useTimeout = async <T> (promise: T | Promise<T>, ms: number): Promi
 export const getSandboxWindowAsync = async (targetEl: Element | undefined = undefined): Promise<Window> => {
   if (typeof document === 'undefined') return {} as any as Window
 
+  if (isGmAvailable('addElement')) {
+    // create iframe using GM_addElement API
+    const iframe = await _GM.addElement('iframe', {})
+    iframe.style.display = 'none'
+    return iframe.contentWindow as Window
+  }
+
   if (!targetEl) {
     return new Promise((resolve) => {
       // You need ads in your pages, right?