WebExtension/background.js

let backgroundPage = browser.extension.getBackgroundPage();

var data;
let i=0;

browser.browserAction.onClicked.addListener(function(event1){
		browser.tabs.create({"url": "home.html"},function(tab){
				browser.runtime.onMessage.addListener(function(request,sender,sendResponse){
						handleMessages(request,sender,sendResponse,tab);
				});
		});
});
function handleMessages(message,sender,sendResponse,tab){
		if(message === "Button_clicked")
				{
				browser.tabs.executeScript(tab.id,{				
						file:"spawn.js"
				});
				console.log(tab);
				console.log(data);
				}
				else if(message === "Content_Loaded")
				{
						console.log("Background: Received Content_Loaded");
						if(i===0)
						{
								browser.tabs.sendMessage(tab.id,"Init");
						}
						else
						{
								browser.tabs.sendMessage(tab.id,data.subscriptions[i].url);
						}
						console.log(i);
				}
				else if(message === "finished")
				{
						i++;
						console.log("background: received next from spawn.js");
						console.log("URL:",data.subscriptions[i].url);
						browser.tabs.update(tab.id,{url : data.subscriptions[i].url});
						browser.tabs.executeScript(tab.id,{				
								file:"spawn.js"
						});

						browser.tabs.sendMessage(tab.id,data.subscriptions[i].url);
				}
		else if(message.status == "FileChange")
		{
				let file = message.file;
				const reader = new FileReader();

				reader.addEventListener("load",()=>{

						data = JSON.parse(reader.result);
						console.log(data);
				},false);
				if(file)
				{
						reader.readAsText(file);
				}
		}
}
//----depreacted -vv
function readUrl()
{		
		let data;
		return  new Promise(resolve => {
		const filePath = "newpipe_subscriptions_202403101004.json";
		var localURL = browser.extension.getURL(filePath);
		fetch(localURL).then((res) => {
								if(!res.ok){
										throw new Error
											(`res error`);
								}
								return res.json();
						})
						.then((data) => {
								for(let i=0;i<i;i++) //wtf why does this work?
								{
										let open=null;
										console.log(data.subscriptions[i].url);
										try{
											open = alert(data.subscriptions[i].url,"_blank");
										}
										catch(e) {InsertError(e.description);}
								}
								console.log(data);
								resolve(data);
						})
						.catch((error)=> console.error("couldnt fetch data",error));
		});
}