Why doesn't setBadgeText change under the if condition?

Question

JavaScript

Hello.
I'm writing a small extension.
There was a need to change the text near the icon ( setBadgeText ) provided that there is an element with the class .red_nor
Actually, what did I do here.
Here is my manifest object

{
  "manifest_version": 2,

  "name": "MyApp",
  "version": "1.0",
  "description": "Description text", 
  "background_page": "background.html",
  "browser_action": {
    "name": "Manipulate DOM",

  "default_icon": {                   
    "38": "lock-icon.png",         
    "19": "icon.png"           

  }

  },
  "background": {
  "scripts": ["background.js", "jquery.min.js"]
  },


  "content_scripts": [ {
    "js": [ "jquery.min.js", "background.js" ],
    "matches": [ "http://*/*", "https://*/*"]
  }]
}

here is my background.js

var succlass = ".red_nor";
if ($(succlass)) {
    console.log("true");
    chrome.browserAction.setBadgeText({text: "yeah"});
} else {
    console.log("false");
}

The console screams
background.js:56 Uncaught TypeError: Cannot read property 'setBadgeText' of undefined
Actually that's understandable, I'm trying to change the browser element in a script that works with content elements.
So what's the correct way to change the browserAction element given content elements?

Answer 1

You need to check like this $(succlass).length:
Even if no object is found, a jquery object will be returned, which is always true.

Answer 2

I don’t know for sure, but if you have Jquery, then in background.js in if you need to write $("succlass"), not just $(succlass)

Answer 3

In general, it seems like I figured it out. The fact is that when writing an application, there is a certain hierarchy, i.e. there is a separate script that works with browser elements, and there is one that works with the content part of the site.
Respectively it is browser_action and content_scripts
Now there is a question. How to pull out the value value in the content form and insert this value into the url of the script that processes the browser element i.e. i have this code

xhr = new XMLHttpRequest();
    xhr.open("GET", "http://example.ru/1466088862.4504/", true);
    xhr.send(null);
    xhr.onreadystatechange = function() {

it is necessary that instead of a link (1466088862.4504/) there is a variable, and the value of the variable is the value of the value that we pulled out in the content?