Google Chrome Extension: jQuery doesn't work in background.js [duplicate] - google-chrome

Question

This question already has answers here:
How to access the webpage DOM/HTML from an extension popup or background script?
(2 answers)
Closed 7 years ago.
For some reason, jQuery doesn't work in my background.js in my Google Chrome extension.
Suppose my plugin tells me all the images on the page. I verified that it gets to the below method OK, but it stops at the jQuery loop.
First, manifest.json: note I'm including jQuery, the file exists:
{
"name": "Gallery",
"version": "0.0.1",
"manifest_version": 2,
"description": "Gallery",
"browser_action": {
"default_icon": "G.png"
},
"background": {
"persistent": true,
"scripts": ["jquery-1.11.2.min.js", "background.js"]
},
"permissions": [
"tabs", "contextMenus", "http://*/*", "https://*/*"
],
"content_scripts": [
{
"matches": [
"http://*/*",
"https://*/*"
],
"css": ["contentstyle.css"],
"js": ["jquery-1.11.2.min.js", "contentscript.js"]
}
],
"icons": {
"32": "G.png"
}
}
background.js uses the jQuery syntax:
chrome.browserAction.onClicked.addListener(scanImages);
function scanImages()
{
// IT GETS HERE - THIS IS OK
alert('Clicked plugin button, about to start looping thru IMG...');
// BUT STOPS HERE: JQUERY DOESN'T EXECUTE
$("img").each(function() {
alert($(this).prop("src"));
});
// ANOTHER JQUERY THAT DOESN'T WORK
alert('Page title = ' + $(document).find("title").text());
}

Answer 1

To access the DOM of any page you need to use content scripts as explained in the comments. Though there is another way of accessing more than one scripts in your background.js.
Add the jquery-1.11.2.min.js in your background.html file.
....
<script type="text/javascript" src="jquery-1.11.2.min.js"></script>
<script type="text/javascript" src="background.js"></script>
....
manifest.json -->
"background": {
"page": "path/to/background.html",
"persistent": true
}
You don't have to define the scripts key also, just define your background.html page and the scripts you want in the head section of the html file. I Hope it helps.