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This code, for some reason causes firefox to not even reconize this script (does not execute it, nor will it show up on debugger sources), can anyone tell me why?

// ==UserScript==
// @name     Unnamed Script 692044
// @version  1
// @grant    GM.setValue
// @grant    GM.getValue
// @include      *
// ==/UserScript==

'use strict';


(function() {
	const ListOfURLs = `
https://google.com
https://wikipedia.org
	`
	window.addEventListener('load', LoadURLAfterTimer)
	
	function LoadURLAfterTimer() {
		console.log("test")
		setTimeout(LoadAnotherPage, 5000)
	}
	
	
	function LoadAnotherPage() {
		let URL_index = await GM.getValue("URLIndex", -1);
		URL_index++
		await GM.setValue("URLIndex", URL_index);
		location.href = ListOfURLs.match(/http(s)?\:\/\/(?!data:)[^\s\"\']+/g)[URL_index] //Code stops executing after this executes.
	}
})();

I'm trying to write a code that causes the browser to go from one URL to another URL after a delay, without opening any additional tabs.

At least one reason - the use of 'await' - does this help? :: https://stackoverflow.com/questions/53939882/why-isnt-await-working-with-async-on-firefox

At least one reason - the use of 'await' - does this help? :: https://stackoverflow.com/questions/53939882/why-isnt-await-working-with-async-on-firefox

Well, another problem: NaN. Updated code.

// ==UserScript==
// @name     Unnamed Script 692044
// @version  1
// @grant    GM.setValue
// @grant    GM.getValue
// @include      *
// ==/UserScript==

'use strict';


(function() {
	const ListOfURLs = `
https://google.com
https://wikipedia.org
	`
	window.addEventListener('load', LoadURLAfterTimer)
	
	function LoadURLAfterTimer() {
		console.log("test")
		setTimeout(LoadAnotherPage, 5000)
	}
	
	
	function LoadAnotherPage() {
		let URL_index = GM.getValue("URLIndex", -1).then();
		URL_index++
		GM.setValue("URLIndex", URL_index).then();
		location.href = ListOfURLs.match(/http(s)?\:\/\/(?!data:)[^\s\"\']+/g)[URL_index] //Code stops executing after this executes.
	}
})();

for some reason, URL_index is supposed to be set to -1 by default if there is no value for it: https://wiki.greasespot.net/GM.getValue