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Javascript : How to analyze potential DOM changes constantly?

I am making an extension for an online chat that has to count the number of new messages sent since the user entered the tchat.
So I'm looking for a JavaScript function that can analyse permanently the tchat page content (specifically the div that contains all messages) and then execute a function. This function will modify the logo badge of the extension and put the number of new messages instead.
I've already tried with MutationObserver, but it doesn't work (maybe because I made mistakes, I don't know). Here's my manifest.json :
{
"manifest_version":2,
"name":"Tchat",
"description":"test",
"version":"0.0.2",
"permissions": [
"tabs"
],
"background": {
"scripts": ["page-reader.js"],
"persistent": true
},
"commands":{
"_execute_browser_action":{
"suggested_key":{
"default":"Ctrl+Q"
}
}
},
"browser_action": {
"default_popup":"index.html",
"default_icon": {
"16": "images/favicon-16x16.png",
"32": "images/favicon-32x32.png",
"144": "images/android-icon-144x144.png"
}
},
"icons": {
"16": "images/favicon-16x16.png",
"32": "images/favicon-32x32.png",
"144": "images/android-icon-144x144.png"
}
}
Here's my page-reader.js file :
var targetNode = null;
var config = {
attributes: true,
childList: true,
subtree: true
};
var MutationObserver = window.MutationObserver;
var numberOfTchatMessages = 0;
var observer = null;
function tchatAnalyser() {
chrome.tabs.query({active: true, lastFocusedWindow: true}, tabs => {
let url = tabs[0].url;
if (url == "here is the tchat url") {
chrome.browserAction.setBadgeBackgroundColor({color: "red"});
chrome.browserAction.setBadgeText({text: "ON"});
targetNode = document.getElementById('zone_tchat');
var callback = function() {
numberOfTchatMessages++;
chrome.browserAction.setBadgeText({text: numberOfTchatMessages.toString()});
};
if (targetNode && MutationObserver) {
observer = new MutationObserver(callback);
observer.observe(targetNode, config);
}
}
else {
chrome.browserAction.setBadgeBackgroundColor({color:"dodgerblue"});
chrome.browserAction.setBadgeText({text:"OFF"});
}
});
}
chrome.tabs.onActivated.addListener(tchatAnalyser);
The logo gets red when I switch to the chat tab, but the text stays at ON… Is there any error in my code ? Is MutationObserver the tool I need ?
Thank you in advance, have a nice day,

Chrome Extension background script not running when published

I have been working on a chrome extension for some time now.
I have a background JS file which is not persistent. While testing the extension locally the background.js file was properly printing results to the console and firing when necessary.
However, once uploaded, it seems that background.js no longer executes when it is supposed to and does not print anything to the console.
Here is the background.js code:
chrome.runtime.onInstalled.addListener(function() {
chrome.tabs.onUpdated.addListener(function(tabId, changeInfo, tab){ // listener for when first loading the page
var url = tab.url;
console.log(url);
if(url != undefined && changeInfo.status == "complete"){ // if the page is done loading, this is done bc .onUpdated has issues with multiple misfires
console.log(url);
var sites = [];
chrome.storage.sync.get({list:[]}, function(data){ // retrieve list of blackListed sites
sites = data.list;
console.log(sites);
for(var i = 0; i < sites.length; i++){
if(tab.url.includes(sites[i])){
chrome.storage.sync.get(['time'], function(data){
if(data.time != null){ // if we are in an active session
chrome.storage.sync.get(['userCausedHours'], function(data2) {
console.log(data2.userCausedHours)
chrome.storage.sync.set({'userCausedHours': data2.userCausedHours + 1}, function() {
console.log('hours = ' + data2.userCausedHours + 1) ;
})
});
}
})
}
}
})
}
});
chrome.tabs.onActivated.addListener(function(activeInfo) { // listener for when flipping back and forth between pages
var sites = [];
chrome.storage.sync.get({list:[]}, function(data){ // retrieve list of blackListed sites
sites = data.list;
console.log(sites);
// how to fetch tab url using activeInfo.tabid
chrome.tabs.get(activeInfo.tabId, function(tab){
console.log(tab.url);
for(var i = 0; i < sites.length; i++){
if(tab.url.includes(sites[i])){
chrome.storage.sync.get(['time'], function(data){
if(data.time != null){ // if we are in an active session
chrome.storage.sync.get(['userCausedHours'], function(data2) {
console.log(data2.userCausedHours)
chrome.storage.sync.set({'userCausedHours': data2.userCausedHours + 1}, function() {
console.log('hours = ' + data2.userCausedHours + 1) ;
})
});
}
})
}
}
});
})
});
});
and here is my manifest:
{
"name": "Serenity",
"version": "1.01",
"description": "Productivity made fun",
"permissions" :["tabs","storage"],
"background" :{
"scripts": ["background.js"],
"persistent": false
},
"options_page": "options.html",
"browser_action": {
"default_popup": "popup.html",
"default_icon": {
"16": "images2/favicon-16x16.png",
"32": "images2/favicon-32x32.png",
"128": "images2/favicon-128.png"
}
},
"icons": {
"16": "images2/favicon-16x16.png",
"32": "images2/favicon-32x32.png",
"128": "images2/favicon-128.png"
},
"manifest_version": 2
}

As stated in the comments, the issue was the fact that I left the .onInstalled around the two listeners for tabs. Moving these listeners into a global context fixed the problem, the .onInstalled isn't necessary for my extension

use chrome extension to open another tab and do something in the DOM

I am trying to build a simple chrome extension to get a value from a page and populate a second page after.
I'm new to chrome extensions, and I'm really only doing this to make something I have to do often simpler.
So I got the part where I open the first page, get the value I need and then I open the second page in another tab. Now I'm not sure how to populate the field.
Since I already have the value on content.js, is it possible to know when the other tab has loaded to just look for the field where i need to put that value in? Or is there another way to do it? I can't get it to work.. I also tried to listen to page loads, but I don't think that will help me, as I'm only interested in one particular page.
Manifest:
{
"manifest_version": 2,
"name": "my Extension",
"version": "1",
"content_scripts": [
{
"matches": [
"<all_urls>"
],
"js": ["jquery-3.2.1.min.js", "content.js"]
}
],
"browser_action": {
"default_icon": "icon.png"
},
"background": {
"scripts": ["background.js"]
}
}
background.js
// Called when the user clicks on the browser action.
chrome.browserAction.onClicked.addListener(function(tab) {
// Send a message to the active tab
chrome.tabs.query({active: true, currentWindow: true}, function(tabs) {
var activeTab = tabs[0];
chrome.tabs.sendMessage(activeTab.id, {"message": "clicked_browser_action"});
});
});
//
chrome.runtime.onMessage.addListener(
function(request, sender, sendResponse) {
if( request.message === "open_new_tab" ) {
chrome.tabs.create({"url": request.url},
function(tab){ alert(tab.id) });
}
}
);
chrome.tabs.onUpdated.addListener(function (tabId , info) {
if (info.status === 'complete') {
chrome.tabs.sendMessage(activeTab.id, {"message": "page_loaded"});
}
});
content.js
chrome.runtime.onMessage.addListener(
function(request, sender, sendResponse) {
if( request.message === "clicked_browser_action" ) {
var myUrl = "http://www.google.com";
var myValue = document.getElementById("thisId").value;
if(myValue ) {
chrome.runtime.sendMessage({
"message": "open_new_tab",
"url": myUrl,
"myValue ": myValue
});
}
}
if( request.message === "page_loaded" ) {
alert("hi");
}
});

Chrome plugin message passing callback undefined

I managed to pass a message between two files/instances, namely my popup and my background scripts, but the callback function still returns undefined, so my popup script does not receive a reply. Can somebody assist me? My code is based on the docs from Google.
Background.js
chrome.runtime.onMessage.addListener(function (sender, sendResponse) {
var resp = {'navURL': "Not set yet"};
if (sender.greeting === "GetURL") {
sendResponse(resp);
}
});
popup.js
function getURL() {
chrome.runtime.sendMessage({
greeting: "GetURL"
},
function (response) {
// RESPONSE IS UNDEFINED //
console.log(response);
alert(response.navURL);
});
}
$("input[type='checkbox']").on('change', function () {
getURL();
});
Manifest.json
{
"name": "FaceBlock",
"description": "This extention gets rid of unwanted content on Facebook like sponsored posts, adds or annoying suggestions. The content you wish to see is enlarged for a better and richer social experience.",
"version": "0.0.1",
"manifest_version": 2,
"content_scripts": [
{
"matches": [
"http://*.facebook.com/*", "https://*.facebook.com/*"],
"css": ["css/popup.css"],
"js": ["js/jquery.min.js", "js/content.js"],
"run_at": "document_end",
"all_frames": true
}],
"options_page": "options.html",
"browser_action": {
"default_icon": "icon.png",
"default_popup": "popup.html",
"default_title": "Faceblock"
},
"permissions": [
"activeTab",
"tabs",
"https://www.facebook.com/*",
"https://ajax.googleapis.com/",
"storage"
],
"background": {
"scripts": ["js/background.js"],
"persistent": false
},
"options_ui": {
// Required.
"page": "popup.html",
// Recommended.
"chrome_style": true
// Not recommended; only provided for backwards compatibility,
// and will be unsupported in a future version of Chrome (TBD).
//"open_in_tab": true
},
"web_accessible_resources": [
"images/faceblock.jpg",
"images/seigaiha.png",
"js/popup.js",
"icon.png",
"js/options.js",
"css/popup.css",
"popup.html",
"options.html"
]
}
Thanks in advance,
Niels Vermeiren
EDIT: I now have the following with the same problem
Background.js
chrome.runtime.onMessage.addListener(function (request, sender, sendResponse) {
sendResponse({msg: "Element " + sender.element + " zijn zichtbaarheid wordt nu: " + sender.checked});
return true;
});
Popup.js
function getCurrentTabUrl(callback) {
return new Promise(function (resolve, reject) {
// https://developer.chrome.com/extensions/tabs#method-query
var queryInfo = {
active: true,
currentWindow: true
};
chrome.tabs.query(queryInfo, function (tabs) {
if (callback(tabs[0].url)) {
return resolve();
} else {
return reject();
}
});
});
}
function changeFacebook(data) {
console.log(data);
chrome.runtime.sendMessage(
"changeFacebook",
data,
function (response //undefined) {
console.log(response.msg); // UNDEFINED
});
}
document.addEventListener('DOMContentLoaded', function () {
var callback = function getCurrentTab(tab) {
if (tab == "https://www.facebook.com/") {
return true;
} else {
return false;
}
}
getCurrentTabUrl(callback).then(function () {
alert('on facebook');
$('.section').hide();
}, function () {
alert('not on facebook');
});
$("input[type='checkbox']").on('change', function () {
var id = $(this).attr('id');
var check = this.checked;
var data = {
'element': id,
'checked': check
};
changeFacebook(data);
});
$('.menuItem').hide();
$('.menuItem:first').show();
jQuery('.navitem').on('click', function () {
var value = $(this).html().toLocaleLowerCase();
jQuery('.menuItem').hide();
jQuery('#' + value).show();
});
});

According to doc here:
https://developer.chrome.com/extensions/runtime#event-onMessage
In your background.js, it should be
chrome.runtime.onMessage.addListener(function (request, sender, sendResponse) {
...
});
Since you are missing the last argument, what you really have is this:
chrome.runtime.onMessage.addListener(function (request, sender) {
...
});
So your code pretty much renamed request => sender, sender => sendResponse.
Therefore, you are trying to invoke sender as a function. But the actual sendResponse callback function is undefined. If you inspect your background page (see tips for how), you should see the error.
Tips:
When developing chrome extension, you can Inspect views: background page in the chrome://extensions page if you have any background page running.
When your popup is opened, you can inspect the popup page just you normally do.
And you can throw debuggers wherever you want, and you will be able to play around with it.
Edit:
So I have tested your code, the issue is just missing argument as I stated above. I also noticed the doc says the first two arguments are optional (not sure what the fuzz that is). But if you change your code to as below, it will work.
Background.js
chrome.runtime.onMessage.addListener(function (request, sender, sendResponse) {
var resp = {'navURL': "Not set yet"};
if (request.greeting === "GetURL") {
sendResponse(resp);
}
});
Popup.js
function getURL() {
chrome.runtime.sendMessage({
greeting: "GetURL"
},
function (response) {
console.log(response);
alert(response.navURL);
});
}
To test it
Go to the background page inspect, and paste in the background page snippet.
Go to the popup page inspect (open your popup, and right click within the popup, then choose inspect)
Paste in the popup page snippet
In the popup page inspect, call getURL()

chrome.tabs.query not executing

My js code just doesnt execute the chrome.tabs.query line. When I went through it stepwise over the debugger it will immediately go to the next executing statement ie return. I looked this up and I understand that this is an asynchronous call but even after waiting the debugger or alert inside the chrome.tabs.query just wouldn't hit. Please help.
/*
Given the name of a beast, get the URL to the corresponding image.
*/
debugger;
function beastNameToURL(beastName) {
switch (beastName) {
case "Save Session":
debugger;
chrome.tabs.query({currentWindow: true}, function(tabs) {
debugger;
alert("1");
tabs.forEach(function(tab){
unsafeWindow.console.log("helllllloooooooooooooooooo");
unsafeWindow.console.log(tab.url);
});
for (var tab of tabs) {
if (tab.active) {
console.log(tab.url);
}
}
});
return;
case "Load Session":
debugger;
return chrome.extension.getURL("beasts/snake.jpg");
case "Turtle":
return chrome.extension.getURL("beasts/turtle.jpg");
}
}
/*
Listen for clicks in the popup.
If the click is not on one of the beasts, return early.
Otherwise, the text content of the node is the name of the beast we want.
Inject the "beastify.js" content script in the active tab.
Then get the active tab and send "beastify.js" a message
containing the URL to the chosen beast's image.
*/
document.addEventListener("click", function(e) {
if (!e.target.classList.contains("btn")) {
return;
}
var chosenBeast = e.target.textContent;
var chosenBeastURL = beastNameToURL(chosenBeast);
chrome.tabs.executeScript(null, {
file: "/content_scripts/beastify.js"
});
chrome.tabs.query({active: true, currentWindow: true}, function(tabs) {
chrome.tabs.sendMessage(tabs[0].id, {beastURL: chosenBeastURL});
});
});
I have also given permissions to tabs in the manifest.
{
"manifest_version": 2,
"name": "Session",
"version": "1.0",
"description": "Adds a browser action icon to the toolbar. Click the button to choose a beast. The active tab's body content is then replaced with a picture of the chosen beast. See https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Examples#beastify",
"homepage_url": "https://github.com/mdn/webextensions-examples/tree/master/beastify",
"icons": {
"48": "icons/beasts-48.png"
},
"applications": {
"gecko": {
"id": "beastify#mozilla.org",
"strict_min_version": "45.0"
}
},
"permissions": [
"activeTab",
"tabs"
],
"browser_action": {
"default_icon": "icons/beasts-32.png",
"default_title": "Session",
"default_popup": "popup/choose_beast.html"
},
"web_accessible_resources": [
"beasts/frog.jpg",
"beasts/turtle.jpg",
"beasts/snake.jpg"
]
}