We Keep Coding

Q: Chrome extension: How to perform the function as soon as open the tab

I'm currently developing an extension that blocks specific users on community sites.
When I enter the community site and click the button in the pop-up window, the specific user's post disappears.
But I want to make this disappear as soon as I enter the community site without pressing a button.
popup.js
let blockUser = document.getElementById("userBlock");
blockUser.addEventListener("click", async () => {
let [tab] = await chrome.tabs.query({ active: true, currentWindow: true });
chrome.scripting.executeScript({
target: { tabId: tab.id },
function: setPageUserBlock,
});
});
function setPageUserBlock() {
chrome.storage.sync.get("blacklist", ({ blacklist }) => {
var lists = document.querySelectorAll("a.vrow");
var users = document.querySelectorAll("span.user-info");
var name;
var m = 6;
for (var i = 5; i < users.length; i++) {
name = users[i].innerText;
if (name == blacklist) {
lists[m].parentNode.removeChild(lists[m]);
}
m += 1;
}
});
}
background.js
let blacklist = 'FTB';
chrome.runtime.onInstalled.addListener(() => {
chrome.storage.sync.set({ blacklist });
});

For this you can use Content Scripts: https://developer.chrome.com/docs/extensions/mv3/content_scripts/
These allow you to put code in a separate file, for example content_script.js, and then in your manifest use
"content_scripts": [
{
"matches": ["http://site-to-block-on.com/*"],
"js": ["content_script.js"]
}
],
And it will load the file as soon as you open that page!
Read through the documentation page, it's a really nice resource to get started. Content Scripts have some quirks, but those are well documented.

Chrome vs. Firefox Extensions

I wrote a simple extension for Firefox. Unfortunately, my friend uses Chrome, and I don't understand why the same code does nothing in Chrome. What's the difference between Firefox's Tabs and Chrome's Tabs? Here's the code:
Manifest.json:
{
"manifest_version": 2,
"name": "customAddon",
"description": "Unsurprisingly, this addon does things.",
"version": "1",
"background": {
"persistent": true,
"scripts": ["customAddon.js"]
},
"permissions": [
"tabs",
"http://*.com/"
]
}
customAddon.js:
chrome.tabs.onUpdated.addListener(function(tabId , info) {
if (info.status == "complete") {
if (window.location.href == 'http://ninjakiwi.com/Games/Action/Play/SAS-Zombie-Assault-4.html') {
var elem = document.getElementById('secondary');
elem.innerHTML = '';
var removeLinks = (function() {
return function(passedElems){
for (i = 0; i < passedElems.length; i++) {
passedElems[i].setAttribute('onclick','return false;');
}}})();
removeLinks(document.getElementsByClassName('group'));
removeLinks(document.getElementsByClassName('nav'));
removeLinks(document.getElementsByClassName('local-skin'));
document.getElementsByClassName('header-bar')[0].setAttribute('style','padding-left:85px; padding-right:-85px;');}}
}
});

Your customAddon.js code runs is a separate, invisible page, called the background page.
Of course, its location.href will never be that URL, and its elements will never match what you expect.
What you really need is a content script. You can set the filter that tells which page it should be loaded in, and then it will execute with access to the page's DOM, which is precisely what you need. No need to use tabs API.

How can I determine if a Chrome extension is in a popup from the content script?

Background
I have a Chrome extension with a browser action to launch index.html in a new tab.
I'd like to update the extension to open index.html in a popup first, and then include a button users can click to optionally open the app in a new tab.
I don't want this button to show when it's not a popup (since it wouldn't make sense), which means the content script needs to know whether it is a popup in order to show the button.
Questions
This is a two part question:
How does a Chrome extension popup know it's a popup?
How do I pass that information to a content script before the popup is rendered?
What I've tried
I've tried to use chrome.extension.getViews in background.js to firstly determine if a popup is open. Then, I send a message to the content script which then shows the button. However I haven't gotten it to work - views is always an empty array, and the message doesn't seem to ever be received by the content script.
Here are the relevant parts of my manifest.json file:
"background": {
"scripts": ["background.js"]
},
"browser_action": {
"default_icon": {
"19": "img/icon19.png",
"38": "img/icon38.png"
},
"default_title": "Super Simple Tasks",
"default_popup": "index.html"
}
And here's what I've been trying in my background.js:
// Get all popups
var views = chrome.extension.getViews({ type: "popup" });
// Send a message if there is a popup
if (views.length > 0){
chrome.tabs.query({active: true, currentWindow: true}, function(tabs){
chrome.tabs.sendMessage(tabs[0].id, {action: "popup_open"}, function(response) {});
});
};
And then in my content script, I listen for the message and then add a class to the body:
// Listen for the message
chrome.extension.onMessage.addListener(function(msg, sender, sendResponse) {
if (msg.action === 'popup_open') {
// My code here to show the button
}
});

After talking with a friend I discovered an elegant solution that doesn't involve messaging or even a background.js script at all.
I can specify ?popup=true in manifest.json and check for that parameter in my extension's content script. Here's the code:
manifest.json now looks like this:
"browser_action": {
"default_icon": {
"19": "img/icon19.png",
"38": "img/icon38.png"
},
"default_title": "Super Simple Tasks",
"default_popup": "index.html?popup=true"
}
The following code in my content script (taken from this answer) checks for ?popup=true. Worth noting that this function can handle multiple URL parameters split by the & character.
function getUrlParameter(sParam) {
var sPageURL = window.location.search.substring(1);
var sURLVariables = sPageURL.split('&');
for (var i = 0; i < sURLVariables.length; i++) {
var sParameterName = sURLVariables[i].split('=');
if (sParameterName[0] == sParam) {
return sParameterName[1];
}
}
}
var isPopup;
isPopup = getUrlParameter('popup') === 'true';
Finally, add a class to the body if it's a popup:
$('body').toggleClass('popup', isPopup)

In the manifest file add a hash to the url:
"browser_action": {
"default_popup": "index.html#popup"
}
In JavaScript:
if (location.hash === '#popup')
// do something awesome!

I needed something similar as i wanted to create some cross-compatible code for all script types.
I found that this worked quite well.
const SCRIPT_TYPE = (() => {
if (chrome && chrome.extension && chrome.extension.getBackgroundPage && chrome.extension.getBackgroundPage() === window) {
return 'BACKGROUND';
} else if (chrome && chrome.extension && chrome.extension.getBackgroundPage && chrome.extension.getBackgroundPage() !== window) {
return 'POPUP';
} else if (!chrome || !chrome.runtime || !chrome.runtime.onMessage) {
return 'WEB';
} else {
return 'CONTENT';
}
})();

chrome.tabs.getCurrent(function(tab) {
if(tab == undefined)
document.getElementById('mButton').style.display = 'inline-block';
});
I initially set the button's display: none; if the returned tab is undefined, means it's not a tab (so it is popup) and then I display button. You can reverse it of course.
======
Well the sending parameter also works, which in that case you won't need to add the query string in the manifest, just adding it in button's click listener would suffice.
btn.addEventListener('click', function() {
chrome.tabs.create({url: "index.html?popup=false"});
});
And then the same process (reading the query string and comparing, etc).
======
Alternatively you can make a copy of index.html say index2.html, remove the button from index.html, use index2.html in the manifest and index.html for button click. :)

Chrome Extension workaround with popup html

My project is a Chrome extension that will do the following.
Push the extension icon.
Popup will appear (from popup.html)
5 buttons will be in the popup.
When you click one of the four buttons, one javascript code will be executed.
close popup window.
So depending on the answer of this post over here
Detect a button click in the browser_action form of a Google Chrome Extension
(big ups to Michael for his enormous help)
This example is only for one button. Created it with only one of my javascript code and works perfect.
But when it comes to put all of the 5 buttons i 've tried to make this kind of coding but it didnt work at all (im new at javascript code so dont hate)
Here are the codes
MANIFEST.JSON
{
"background": {
"scripts": [ "background.js" ]
},
"browser_action": {
"default_icon": "img/icon.png",
"default_title": "TITLE",
"default_popup": "popup.html"
},
"icons": {
"128": "img/icon_128.png",
"19": "img/icon19.png",
"38": "img/icon38.png",
"48": "img/icon_48_2.png"
},
"manifest_version": 2,
"name": " NAME",
"description": " DESCR ",
"permissions": [ "activeTab" ],
"version": "2.0"
}
POPUP.HTML
<html>
<head>
<script src="popup.js"></script>
<style type="text/css" media="screen">
body { min-width:250px; text-align: center; }
#click-me-l { font-size: 20px; }
#click-me-f { font-size: 20px; }
</style>
</head>
<body>
<button id='click-me-l'>Click1</button>
<button id='click-me-f'>Click2</button>
</body>
</html>
POPUP.JS
function clickHandler(e) {
chrome.extension.sendMessage({directive: "popup-click-l"}, function(response) {
this.close(); // close the popup when the background finishes processing request
});
}
document.addEventListener('DOMContentLoaded', function () {
document.getElementById('click-me-l').addEventListener('click', clickHandler);
})
function clickHandler(e) {
chrome.extension.sendMessage({directive: "popup-click-f"}, function(response) {
this.close(); // close the popup when the background finishes processing request
});
}
document.addEventListener('DOMContentLoaded', function () {
document.getElementById('click-me-f').addEventListener('click', clickHandler);
})
BACKGROUND.JS
chrome.extension.onMessage.addListener(
function(request, sender, sendResponse) {
switch (request.directive) {
case 1 "popup-click-l":
// execute the content script
chrome.tabs.executeScript(null, { // defaults to the current tab
file: "script1.js", // script to inject into page and run in sandbox
allFrames: true // This injects script into iframes in the page and doesn't work before 4.0.266.0.
});
case 2 "popup-click-f":
// execute the content script
chrome.tabs.executeScript(null, { // defaults to the current tab
file: "script2.js", // script to inject into page and run in sandbox
allFrames: true // This injects script into iframes in the page and doesn't work before 4.0.266.0.
});
sendResponse({}); // sending back empty response to sender
break;
default:
// helps debug when request directive doesn't match
alert("Unmatched request of '" + request + "' from script to background.js from " + sender);
}
}
);
So the codes in the link are working PERFECT for only 1 button.
in this example i am trying to make it work for 2 buttons but i cant find what im doing wrong. If anyone has any idea i would appreciate it.
Thanks a lot for your time!!!
(UPDATE 2. Updated codes for 2 buttons but not working.)

You’re defining clickHandler twice, so only the second one counts. One fix would be:
function clickHandler(e) {
chrome.extension.sendMessage({"directive": e.target.id}, function(response) {
this.close(); // close the popup when the background finishes processing request
});
}
In general, you’re repeating yourself too much. You could combine your DOMContentLoaded events into one:
document.addEventListener('DOMContentLoaded', function () {
document.getElementById('click-me-l').addEventListener('click', clickHandler);
document.getElementById('click-me-f').addEventListener('click', clickHandler);
})
but even better would be to put all the buttons into an array, so that popup.js is now:
function clickHandler(e) {
chrome.extension.sendMessage({"directive": e.target.id}, function(response) {
this.close(); // close the popup when the background finishes processing request
});
}
document.addEventListener('DOMContentLoaded', function () {
var buttons = document.getElementsByTagName("button");
for ( var i = 0 ; i < buttons.length ; i++ ) {
buttons[i].addEventListener('click',clickHandler);
}
})
(And I’d recommend button { font-size: 20px; } in your style instead of five separate ids.)
Finally, your switch statement is buggy. Once you start a case, you’ll keep going until you get to a break, so that case "popup-click-l" hits both cases. You could have a separate executeScript for each case, but even better would be to assign to fileName based on the case, and have a single injection at the end. Or best of all would be to have a javascript object define which files go with which ids, so that background.js is now:
chrome.extension.onMessage.addListener(
function(request, sender, sendResponse) {
var injected = {
"click-me-l": "script1.js",
"click-me-f": "script2.js"
};
chrome.tabs.executeScript(null, {
"file": injected[request.directive],
"allFrames": true
});
sendResponse({});
}
);
Fundamentally, this comes back to a point I made in a comment: browser extensions are a bad way to learn javascript, because you’re learning two separate things at the same time. Your difficulties with switch, {}, and generally following the code is a javascript problem. Not seeing when the console tells you about syntax errors is more of a browser extension problem. And your biggest problem is that you’re not seeing which error is which.

how do i toggle on/off content_scripts in a google extension?

I have this simple extension, it displays icon on chrome's toolbar and shows a enable/disable button. i want to add function to the button to disable or enable the content_script.js which fires on visiting google website:
popup.js
var setLayout = function(){
var list = document.createElement('ul');
var enable = document.createElement('li');
enable.appendChild(document.createTextNode('Enable Script'));
enable.onclick = function(){toggle(0)};
var disable = document.createElement('li');
disable.appendChild(document.createTextNode('Disable Script'));
disable.onclick = function(){toggle(1)};
list.appendChild(disable);
document.body.appendChild(list);
function toggle(n){
list.removeChild( n == 0 ? enable : disable);
list.appendChild(n == 0 ? disable : enable);
}
};
document.addEventListener('DOMContentLoaded', setLayout, false);
manifest.json
{
"manifest_version": 2,
"name": "test",
"description": "test",
"version": "1.0",
"browser_action": {
"default_icon": "icon.png",
"default_popup": "popup.html"
},
"content_scripts": [
{
"matches": ["https://www.google.co.uk/"],
"js": ["content_scripts.js"]
}
]
}
content_scripts.js
(function(){
alert('hello');
})();
i'm new to google extensions and have no idea how to do that, i thought about changing the manifist after clicking disable/enable buttons but couldn't find the right command to do so after reading the documentations on google website!
any help would be greately appreciated.

After some research i figured out how to solve this by using backround pages, sendMessage and localstorage.
background pages work as a communicator between popup.js and content_scripts.js, they are on two different documents and it's not possible to pass variables between them directly.
To enable background page in mamifest i added:
"background": {
"scripts": ["background.js"],
"persistent": true
},
localstorage save variables locally and remember them even when the browser is closed and opened again, so when enable/disable button is clicked it set localStorage['status'] = 1/0 which can be accessed through background.js and passed to content_scripts.js.
To set localStorage variable i added to popup.js:
if(!localStorage.status) localStorage['status'] = 1;
toggle(2);
enable.onclick = function(){toggle(0)};
disable.onclick = function(){toggle(1)};
function toggle(n){
if((n == 0) && (enable.parentNode == list)){
list.removeChild(enable);
list.appendChild(disable);
localStorage.status = 1;
}else if((n == 1) && (disable.parentNode == list)){
list.removeChild(disable);
list.appendChild(enable);
localStorage.status = 0;
}else if((n == 2) && (!list.hasChildNodes())){
list.appendChild((localStorage.status == 1) ? disable : enable);
chrome.browserAction.setIcon({path: (localStorage.status == 1) ? "icons/icon19.png" : "icons/icon19_disabled.png"});
}else{
return;
}
}
To pass localStorage.status to content_scripts.js i had to use sendMessage on content_scrips.js which on loaded send request message to background.js, and onMessage on background.js which listens to requests and send response to content_scripts.js with the localStorage.status value.
background.js:
chrome.runtime.onMessage.addListener(
function(request, sender, sendResponse) {
if (request.type == "status") sendResponse({status: localStorage.status});
});
content_scripts.js
var fn = function(){...};
chrome.runtime.sendMessage({type: "status"}, function(response) {
if(response.status == 1) fn();
return;
});
That's it, hope someone find it useful.

Try injecting the content script using code rather than the manifest file, something like this:
chrome.tabs.executeScript(null, {file: "content_script.js"});
You can then use message passing between the background page and your content script to decide whether or not to inject the content script, or perhaps an if statement in the content script itself that only runs when a flag set by the extension's action button.
You can use a browser action event to detect when the action button is pressed.