CODE EXAMPLE FOR JAVASCRIPT

Add jquery in extension

{
  "name": "MyExtension",
  "version": "0.1",
  "description": "blah blah",
  "background_page": "background.html",
  "content_scripts": [
    {
      "matches": ["http://*/*","https://*/*"],
      "css": ["extension.css"],
      "js": ["jquery-1.4.2.js", "extension.js"]
    }
  ]
}