Hi 
I'm fairly new to creating extensions. 
So far I've spent 3-4 days/week, and so far I've got it to display one thing on all URLs, but another information on a specified URL that matches.
in my manifest.json file i have:-
=========================
 "content_scripts":[
    {
      "matches":["
https://www.myURL.com"],
      "js":["content.js"]
    }
   ],
 "action": {
    "default_popup": "hello.html",
    "default_icon": "hello_extensions.png"
  },
  "permissions":["tabs"]
"background": {
  "scripts": ["background/background.js"]
}
=========================
Now THIS does work, and the content.js file is going.. if it is on the specified URL.
hello.html displays on all other URLS.
PROBLEM: 
when I'm adding my background.js file information to manifest, Manifest doesn't work. 
ERROR;
Manifest is not valid JSON. Line: 22, column: 1, Syntax error.
LINE:  "background": {
Can anyone assist with this?
Also - Once I get background going, is there a small tutorial on 
a) loop through all the files being downloaded by the user.
b) if it is a json file, loop through the file for specified text.
I'm used to PHP, so these commands may be useful to me:  
- preg_match,  and - extract small information from LONG lines of text.
- save / store (and view) information into the app's memory (user's PC?)
Any guidance appreciated.