alerts on multiple URLs depending on whether URL is listed in a given file

extension/js/background.js

-var debug = 0;
-var stop_url = "https://www.google.com/"
+var debug = 1;
+
+var urls_to_compare = readTextFile("urls.txt");
+
+/* this code base courtesty of https://stackoverflow.com/questions/14446447/javascript-read-local-text-file#14446538*/
+
+function readTextFile(file){
+	var rawFile = new XMLHttpRequest();
+	rawFile.open("GET", file, false);
+	rawFile.onreadystatechange = function (){
+		if(rawFile.readyState === 4){ 
+			if(rawFile.status === 200 || rawFile.status == 0){
+				lines = rawFile.responseText.split("\n");
+		}}}
+	rawFile.send(null);
+	return(lines);}
+
+function is_a_stop(possible_stop_urls, current_url){
+	if (debug){
+		console.log("URLs to compare");
+		console.log(possible_stop_urls);
+		console.log(possible_stop_urls.length);
+		console.log("current URL:");
+		console.log(current_url);}
+	for (i = 0; i<possible_stop_urls.length; i++){
+		if (current_url == possible_stop_urls[i]){
+			console.log("stop url detected");
+			return(true);}}
+	return(false);}
 
 chrome.tabs.onUpdated.addListener(function (tabID, changeInfo, tab) {
+	if (debug){ console.log(urls_to_compare);}
 	var url;
 
 	chrome.tabs.query({'active': true, 'lastFocusedWindow': true}, function (tabs) {
-    	url = tabs[0].url;
-	if (debug){ console.log(url);}
-
-	if (changeInfo.status=='complete'){
-		if (url==stop_url){
-    			chrome.tabs.sendMessage(tab.id, { action: 'saySomething' });
-			if (debug) {console.log("background something");}} } 
+		url = tabs[0].url;
+		if (debug){ console.log(url);}
+		if (changeInfo.status=='complete'){
+			if (is_a_stop(urls_to_compare, url)){
+				chrome.tabs.sendMessage(tab.id, { action: 'match' });
+				if (debug) {console.log("background found match");}} } 
 });});

extension/js/content.js

 chrome.runtime.onMessage.addListener(function (msg) {
     /* We received a message, let's do as instructed */
-    if (msg.action == 'saySomething') {
+    if (msg.action == 'match') {
         window.alert('Google!');
     }
 });