how to get access to window object of current website in chrome extension

I’m working on a browser extension that needs access to the “login” key from the “window” object of the active tab.

There is my manifeset.json

 {...}
"permissions": [
    "activeTab",
    "storage",
    "scripting",
    "tabs"
  ],
  "background": {
    "service_worker": "background.js",
    "type": "module"
  },
  "content_scripts": [
    {
      "matches": ["<all_urls>"],
      "js": ["content.js"]
    }
  ],

Additional I have popup.js attached to popup.html, and I need to have window.login in that file.
Currently everytime when I tried to get access to window, there is a window before all react loaded so there is almost empty window. I used window.onload and it didn’t work,